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Software is hard (yes, even in an era of vibe coding), and systems software — the silent engine room of modern infrastructure — is especially so. By design, systems software provides an abstraction for programs, insulating programmers from the filthy details that lie beneath; piercing that abstraction to implement the underlying system is to embrace those details and their gnarly implications. Moreover, the expectation for systems software is (rightly) perfection; a system that is merely functional can be deceptively distant from the robustness required of foundational software. Systems software isn’t the only kind of hard software, of course, and indeed software can be difficult just by nature of its scope and composition: it is hard to build software that is just… big. Software that consists of many different modules and components built by multiple people over an extended period of time is known as programming in the large, and its difficulties extend beyond the mere implementation challenges of systems software. Because the difficulties with developing systems software are broadly orthogonal to those of programming in the large, intersecting these two challenges — that is, developing systems software in the large — is to take on the most grueling of projects: it is the stuff of which mythical man months are literally made. Why would anyone ever develop such a system? Because they are often necessary to tackle software’s equivalents of the wicked problem: problems that are not only never completely solved, but also not even really understood until implementation is well underway. There are not pat answers for developing these systems — nor, infamously, silver bullets — they’re just… brutal. This is on my mind because of a talk that we had at OxCon last week. OxCon is our affectionate name for the annual Oxide meetup here in Emeryville, and it’s a highlight of the year for everyone at Oxide. This year more than lived up to our high expectations, replete with cameos from the extraordinary IBM 26 Interpreting Card Punch and the Oakland Ballers. At OxCon we like to both reflect back and look forward, so in that spirit, we asked Oxide engineer Dave Pacheco if he might be willing to present on the project he’s been leading the charge on for the past two years: software update. When we shipped the first Oxide rack two years ago, it had the minimum functionality necessary to update all its software in the field. Our priority was to make this update mechanism robust over all else, and we succeeded in the sense that it is indeed robust — but the experience is not yet the seamless, self-service facility that we have envisioned. Software update for the Oxide rack is exactly the kind of wicked problem that necessitates systems software in the large: it is not merely dynamically overhauling a distributed system, but doing so while remaining operable in the liminal state between the old software and the new. Compounding this was the urgency we felt: delivering self-service update is essential to realize our vision of the cloud experience on premises, and our customers needed it as soon as we could deliver it. As if this weren’t enough, the Oxide update problem has an acute constraint not faced by the public clouds: we need to be able to deliver updates across an air gap — we cannot rely on the public cloud’s hidden crutch of operators and runbooks. It is a problem so wicked, you can practically hear it cackle. Despite the thorniness of the problem, Dave and team had managed to achieve the ambitious milestones that they had set for themselves at OxCon last year, and I was naturally excited for his presentation this year. That said, I wasn’t ready for what was coming: Dave not only described the tremendous work on software update (delving into both the multi-year history of the project and the significant progress since the last OxCon), but also reflected on leading the software update project itself. The result was an absolutely extraordinary talk, not just on the mechanics of software essential to Oxide, but on the unique challenges of systems software in the large. Dave’s talk dripped with hard-won wisdom, running the gamut from maintaining focus (and the looming specter of what Dave calls "organizational procrastination") to fighting scope creep and the mechanics of specific technical decisions. We felt Dave’s talk to be too good to be kept to ourselves — and thanks to our transparency, nothing in it needs to be secret; we are thrilled to be able to make it generally available: This talk is a must watch for anyone doing systems software in the large, containing within it the kind of lessons that are often only learned the hard way. While we think it’s valuable for everyone, should you be the kind of sicko inexplicably drawn to exactly the kind of nasty problems that Dave describes, consider joining us — there is more systems software in the large to be done at Oxide!
How it started Four years ago, we were struggling to hire. Our team was small (~23 employees), and we knew that we needed many more people to execute on our audacious vision. While we had had success hiring in our personal networks, those networks now felt tapped; we needed to get further afield. As is our wont, we got together as a team and brainstormed: how could we get a bigger and broader applicant pool? One of our engineers, Sean, shared some personal experience: that Oxide’s principles and values were very personally important to him — but that when he explained them to people unfamiliar with the company, they were (understandably?) dismissed as corporate claptrap. Sean had found, however, that there was one surefire way to cut through the skepticism: to explain our approach to compensation. Maybe, Sean wondered, we should talk about it publicly? "I could certainly write a blog entry explaining it," I offered. At this suggestion, the team practically lunged with enthusiasm: the reaction was so uniformly positive that I have to assume that everyone was sick of explaining this most idiosyncratic aspect of Oxide to friends and family. So what was the big deal about our compensation? Well, as a I wrote in the resulting piece, Compensation as a Reflection of Values, our compensation is not merely transparent, but uniform. The piece — unsurprisingly, given the evergreen hot topic that is compensation — got a ton of attention. While some of that attention was negative (despite the piece trying to frontrun every HN hater!), much of it was positive — and everyone seemed to be at least intrigued. And in terms of its initial purpose, the piece succeeded beyond our wildest imagination: it brought a surge of new folks interested in the company. Best of all, the people new to Oxide were interested for all of the right reasons: not the compensation per se, but for the values that the compensation represents. The deeper they dug, the more they found to like — and many who learned about Oxide for the first time through that blog entry we now count as long-time, cherished colleagues. That blog entry was a long time ago now, and today we have ~75 employees (and a shipping product!); how is our compensation model working out for us? How it’s going Before we get into our deeper findings, two updates that are so important that we have updated the blog entry itself. First, the dollar figure itself continues to increase over time (as of this writing in 2025, $207,264); things definitely haven’t gotten (and aren’t getting!) any cheaper. And second, we did introduce variable compensation for some sales roles. Yes, those roles can make more than the rest of us — but they can also make less, too. And, importantly: if/when those folks are making more than the rest of us, it’s because they’re selling a lot — a result that can be celebrated by everyone! Those critical updates out of the way, how is it working? There have been a lot of surprises along the way, mostly (all?) of the positive variety. A couple of things that we have learned: People take their own performance really seriously. When some outsiders hear about our compensation model, they insist that it can’t possibly work because "everyone will slack off." I have come to find this concern to be more revealing of the person making the objection than of our model, as our experience has been in fact the opposite: in my one-on-one conversations with team members, a frequent subject of conversation is people who are concerned that they aren’t doing enough (or that they aren’t doing the right thing, or that their work is progressing slower than they would like). I find my job is often to help quiet this inner critic while at the same time stoking what I feel is a healthy urge: when one holds one’s colleagues in high regard, there is an especially strong desire to help contribute — to prove oneself worthy of a superlative team. Our model allows people to focus on their own contribution (whatever it might be). People take hiring really seriously. When evaluating a peer (rather than a subordinate), one naturally has high expectations — and because (in the sense of our wages, anyway) everyone at Oxide is a peer, it shouldn’t be surprising that folks have very high expectations for potential future colleagues. And because the Oxide hiring process is writing intensive, it allows for candidates to be thoroughly reviewed by Oxide employees — who are tough graders! It is, bluntly, really hard to get a job at Oxide. It allows us to internalize the importance of different roles. One of the more incredible (and disturbingly frequent) objections I have heard is: "But is that what you’ll pay support folks?" I continue to find this question offensive, but I no longer find it surprising: the specific dismissal of support roles reveals a widespread and corrosive devaluation of those closest to customers. My rejoinder is simple: think of the best support engineers you’ve worked with; what were they worth? Anyone who has shipped complex systems knows these extraordinary people — calm under fire, deeply technical, brilliantly resourceful, profoundly empathetic — are invaluable to the business. So what if you built a team entirely of folks like that? The response has usually been: well, sure, if you’re going to only hire those folks. Yeah, we are — and we have! It allows for fearless versatility. A bit of a corollary to the above, but subtly different: even though we (certainly!) hire and select for certain roles, our uniform compensation means we can in fact think primarily in terms of people unconfined by those roles. That is, we can be very fluid about what we’re working on, without fear of how it will affect a perceived career trajectory. As a concrete example: we had a large customer that wanted to put in place a program for some of the additional work they wanted to see in the product. The complexity of their needs required dedicated program management resources that we couldn’t spare, and in another more static company we would have perhaps looked to hire. But in our case, two folks came together — CJ from operations, and Izzy from support — and did something together that was in some regards new to both of them (and was neither of their putative full-time jobs!) The result was indisputably successful: the customer loved the results, and two terrific people got a chance to work closely together without worrying about who was dotted-lined to whom. It has allowed us to organizationally scale. Many organizations describe themselves as flat, and a reasonable rebuttal to this are the "shadow hierarchies" created by the tyranny of structurelessness. And indeed, if one were to read (say) Valve’s (in)famous handbook, the autonomy seems great — but the stack ranking decidedly less so, especially because the handbook is conspicuously silent on the subject of compensation. (Unsurprisingly, compensation was weaponized at Valve, which descended into toxic cliquishness.) While we believe that autonomy is important to do one’s best work, we also have a clear structure at Oxide in that Steve Tuck (Oxide co-founder and CEO) is in charge. He has to be: he is held accountable to our investors — and he must have the latitude to make decisions. Under Steve, it is true that we don’t have layers of middle management. Might we need some in the future? Perhaps, but what fraction of middle management in a company is dedicated to — at some level — determining who gets what in terms of compensation? What happens when you eliminate that burden completely? It frees us to both lead and follow. We expect that every Oxide employee has the capacity to lead others — and we tap this capacity frequently. Of course, a company in which everyone is trying to direct all traffic all the time would be a madhouse, so we also very much rely on following one another too! Just as our compensation model allows us to internalize the values of different roles, it allows us to appreciate the value of both leading and following, and empowers us each with the judgement to know when to do which. This isn’t always easy or free of ambiguity, but this particular dimension of our versatility has been essential — and our compensation model serves to encourage it. It causes us to hire carefully and deliberately. Of course, one should always hire carefully and deliberately, but this often isn’t the case — and many a startup has been ruined by reckless expansion of headcount. One of the roots of this can be found in a dirty open secret of Silicon Valley middle management: its ranks are taught to grade their career by the number of reports in their organization. Just as if you were to compensate software engineers based on the number of lines of code they wrote, this results in perverse incentives and predictable disasters — and any Silicon Valley vet will have plenty of horror stories of middle management jockeying for reqs or reorgs when they should have been focusing on product and customers. When you can eliminate middle management, you eliminate this incentive. We grow the team not because of someone’s animal urges to have the largest possible organization, but rather because we are at a point where adding people will allow us to better serve our market and customers. It liberates feedback from compensation. Feedback is, of course, very important: we all want to know when and where we’re doing the right thing! And of course, we want to know too where there is opportunity for improvement. However, Silicon Valley has historically tied feedback so tightly to compensation that it has ceased to even pretend to be constructive: if it needs to be said, performance review processes aren’t, in fact, about improving the performance of the team, but rather quantifying and stack-ranking that performance for purposes of compensation. When compensation is moved aside, there is a kind of liberation for feedback itself: because feedback is now entirely earnest, it can be expressed and received thoughtfully. It allows people to focus on doing the right thing. In a world of traditional, compensation-tied performance review, the organizational priority is around those things that affect compensation — even at the expense of activity that clearly benefits the company. This leads to all sorts of wild phenomena, and most technology workers will be able to tell stories of doing things that were clearly right for the company, but having to hide it from management that thought only narrowly in terms of their own stated KPIs and MBOs. By contrast, over and over (and over!) again, we have found that people do the right thing at Oxide — even if (especially if?) no one is looking. The beneficiary of that right thing? More often than not, it’s our customers, who have uniformly praised the team for going above and beyond. It allows us to focus on the work that matters. Relatedly, when compensation is non-uniform, the process to figure out (and maintain) that non-uniformity is laborious. All of that work — of line workers assembling packets explaining themselves, of managers arming themselves with those packets to fight in the arena of organizational combat, and then of those same packets ultimately being regurgitated back onto something called a review — is work. Assuming such a process is executed perfectly (something which I suppose is possible in the abstract, even though I personally have never seen it), this is work that does not in fact advance the mission of the company. Not having variable compensation gives us all of that time and energy back to do the actual work — the stuff that matters. It has stoked an extraordinary sense of teamwork. For me personally — and as I relayed on an episode of Software Misadventures — the highlights of my career have been being a part of an extraordinary team. The currency of a team is mutual trust, and while uniform compensation certainly isn’t the only way to achieve that trust, boy does it ever help! As Steve and I have told one another more times that we can count: we are so lucky to work on this team, with its extraordinary depth and breadth. While our findings have been very positive, I would still reiterate what we said four years ago: we don’t know what the future holds, and it’s easier to make an unwavering commitment to the transparency rather than the uniformity. That said, the uniformity has had so many positive ramifications that the model feels more important than ever. We are beyond the point of this being a curiosity; it’s been essential for building a mission-focused team taking on a problem larger than ourselves. So it’s not a fit for everyone — but if you are seeking an extraordinary team solving hard problems in service to customers, consider Oxide!
Sometime in late 2007, we had the idea of a DTrace conference. Or really, more of a meetup; from the primordial e-mail I sent: The goal here, by the way, is not a DTrace user group, but more of a face-to-face meeting with people actively involved in DTrace — either by porting it to another system, by integrating probes into higher level environments, by building higher-level tools on top of DTrace or by using it heavily and/or in a critical role. That said, we also don’t want to be exclusionary, so our thinking is that the only true requirement for attending is that everyone must be prepared to speak informally for 15 mins or so on what they are doing with DTrace, any limitations that they have encountered, and some ideas for the future. We’re thinking that this is going to be on the order of 15-30 people (though more would be a good problem to have — we’ll track it if necessary), that it will be one full day (breakfast in the morning through drinks into the evening), and that we’re going to host it here at our offices in San Francisco sometime in March 2008. This same note also included some suggested names for the gathering, including what in hindsight seems a clear winner: DTrace Bi-Mon-Sci-Fi-Con. As if knowing that I should leave an explanatory note to my future self as to why this name was not selected, my past self fortunately clarified: "before everyone clamors for the obvious Bi-Mon-Sci-Fi-Con, you should know that most Millennials don’t (sadly) get the reference." (While I disagree with the judgement of my past self, it at least indicates that at some point I cared if anyone got the reference.) We settled on a much more obscure reference, and had the first dtrace.conf in March 2008. Befitting the style of the time, it was an unconference (a term that may well have hit its apogee in 2008) that you signed up to attend by editing a wiki. More surprising given the year (and thanks entirely to attendee Ben Rockwood), it was recorded — though this is so long ago that I referred to it as video taping (and with none of the participants mic’d, I’m afraid the quality isn’t very good). The conference, however, was terrific, viz. the reports of Adam, Keith and Stephen (all somehow still online nearly two decades later). If anything, it was a little too good: we realized that we couldn’t recreate the magic, and we demurred on making it an annual event. Years passed, and memories faded. By 2012, it felt like we wanted to get folks together again, now under a post-lawnmower corporate aegis in Joyent. The resulting dtrace.conf(12) was a success, and the Olympiad cadence felt like the right one; we did it again four years later at dtrace.conf(16). In 2020, we came back together for a new adventure — and the DTrace Olympiad was not lost on Adam. Alas, dtrace.conf(20) — like the Olympics themselves — was cancelled, if implicitly. Unlike the Olympics, however, it was not to be rescheduled. More years passed and DTrace continued to prove its utility at Oxide; last year when Adam and I did our "DTrace at 20" episode of Oxide and Friends, we vowed to hold dtrace.conf(24) — and a few months ago, we set our date to be December 11th. At first we assumed we would do something similar to our earlier conferences: a one-day participant-run conference, at the Oxide office in Emeryville. But times have changed: thanks to the rise of remote work, technologists are much more dispersed — and many more people would need to travel for dtrace.conf(24) than in previous DTrace Olympiads. Travel hasn’t become any cheaper since 2008, and the cost (and inconvenience) was clearly going to limit attendance. The dilemma for our small meetup highlights the changing dynamics in tech conferences in general: with talks all recorded and made publicly available after the conference, how does one justify attending a conference in person? There can be reasonable answers to that question, of course: it may be the hallway track, or the expo hall, or the after-hours socializing, or perhaps some other special conference experience. But it’s also not surprising that some conferences — especially ones really focused on technical content — have decided that they are better off doing as conference giant O’Reilly Media did, and going exclusively online. And without the need to feed and shelter participants, the logistics for running a conference become much more tenable — and the price point can be lowered to the point that even highly produced conferences like P99 CONF can be made freely available. This, in turn, leads to much greater attendance — and a network effect that can get back some of what one might lose going online. In particular, using chat as the hallway track can be more much effective (and is certainly more scalable!) than the actual physical hallways at a conference. For conferences in general, there is a conversation to be had here (and as a teaser, Adam and I are going to talk about it with Stephen O’Grady and Theo Schlossnagle on Oxide and Friends next week, but for our quirky, one-day, Olympiad-cadence dtrace.conf, the decision was pretty easy: there was much more to be gained than lost by going exclusively on-line. So dtrace.conf(24) is coming up next week, and it’s available to everyone. In terms of platform, we’re going to try to keep that pretty simple: we’re going to use Google Meet for the actual presenters, which we will stream in real-time to YouTube — and we’ll use the Oxide Discord for all chat. We’re hoping you’ll join us on December 11th — and if you want to talk about DTrace or a DTrace-adjacent topic, we’d love for you to present! Keeping to the unconference style, if you would like to present, please indicate your topic in the #session-topics Discord channel so we can get the agenda fleshed out. While we’re excited to be online, there are some historical accoutrements of conferences that we didn’t want to give up. First, we have a tradition of t-shirts with dtrace.conf. Thanks to our designer Ben Leonard, we have a banger of a t-shirt, capturing the spirit of our original dtrace.conf(08) shirt but with an Oxide twist. It’s (obviously) harder to make those free but we have tried to price them reasonably. You can get your t-shirt by adding it to your (free) dtrace.conf ticket. (And for those who present at dtrace.conf, your shirt is on us — we’ll send you a coupon code!) Second, for those who can make their way to the East Bay and want some hangout time, we are going to have an après conference social event at the Oxide office starting at 5p. We’re charging something nominal for that too (and like the t-shirt, you pay for that via your dtrace.conf ticket); we’ll have some food and drinks and an Oxide hardware tour for the curious — and (of course?) there will be Fishpong. Much has changed since I sent that e-mail 17 years ago — but the shared values and disposition that brought together our small community continue to endure; we look forward to seeing everyone (virtually) at dtrace.conf(24)!
Here’s a sobering thought: today, data centers already consume 1-2% of the world’s power, and that percentage will likely rise to 3-4% by the end of the decade. According to Goldman Sachs research, that rise will include a doubling in data center carbon dioxide emissions. As the data and AI boom progresses, this thirst for power shows no signs of slowing down anytime soon. Two key challenges quickly become evident for the 85% of IT that currently lives on-premises. How can organizations reduce power consumption and corresponding carbon emissions? How can organizations keep pace with AI innovation as existing data centers run out of available power? Figure 1. Masanet et al. (2020), Cisco, IEA, Goldman Sachs Research Rack-scale design is critical to improved data center efficiency Traditional data center IT consumes so much power because the fundamental unit of compute is an individual server; like a house where rooms were built one at a time, with each room having its own central AC unit, gas furnace, and electrical panel. Individual rackmount servers are stacked together, each with their own AC power supplies, cooling fans, and power management. They are then paired with storage appliances and network switches that communicate at arm’s length, not designed as a cohesive whole. This approach fundamentally limits organizations' ability to maintain sustainable, high-efficiency computing systems. Of course, hyperscale public cloud providers did not design their data center systems this way. Instead, they operate like a carefully planned smart home where everything is designed to work together cohesively and is operated by software that understands the home’s systems end-to-end. High-efficiency, rack-scale computers are deployed at scale and operate as a single unit with integrated storage and networking to support elastic cloud computing services. This modern archietecture is made available to the market as public cloud, but that rental-only model is ill-fit for many business needs. Compared to a popular rackmount server vendor, Oxide is able to fill our specialized racks with 32 AMD Milan sleds and highly-available network switches using less than 15kW per rack, doubling the compute density in a typical data center. With just 16 of the alternative 1U servers and equivalent network switches, over 16kW of power is required per rack, leading to only 1,024 CPU cores vs Oxide’s 2,048. Extracting more useful compute from each kW of power and square foot of data center space is key to the future effectiveness of on-premises computing. At Oxide, we’ve taken this lesson in advancing rack-scale design, improved upon it in several ways, and made it available for every organization to purchase and operate anywhere in the world without a tether back to the public cloud. Our Cloud Computer treats the entire rack as a single, unified computer rather than a collection of independent parts, achieving unprecedented power efficiency. By designing the hardware and software together, we’ve eliminated unnecessary components and optimized every aspect of system operation through a control plane with visibility to end-to-end operations. When we started Oxide, the DC bus bar stood as one of the most glaring differences between the rack-scale machines at the hyperscalers and the rack-and-stack servers that the rest of the market was stuck with. That a relatively simple piece of copper was unavailable to commercial buyers — despite being unequivocally the right way to build it! — represented everything wrong with the legacy approach. The bus bar in the Oxide Cloud Computer is not merely more efficient, it is a concrete embodiment of the tremendous gains from designing at rack-scale, and by integrating hardware with software. — Bryan Cantrill The improvements we’re seeing are rooted in technical innovation Replacing low-efficiency AC power supplies with a high-efficiency DC Bus Bar This eliminates the 70 total AC power supplies found in an equivalent legacy server rack within 32 servers, two top-of-rack switches, and one out-of-band switch, each with two AC power supplies. This power shelf also ensures the load is balanced across phases, something that’s impossible with traditional power distribution units found in legacy server racks. Bigger fans = bigger efficiency gains using 12x less energy than legacy servers, which each contain as many as 7 fans, which must work much harder to move air over system components. Purpose-built for power efficiency less restrictive airflow than legacy servers by eliminating extraneous components like PCIe risers, storage backplanes, and more. Legacy servers need many optional components like these because they could be used for any number of tasks, such as point-of-sale systems, data center servers, or network-attached-storage (NAS) systems. Still, they were never designed optimally for any one of those tasks. The Oxide Cloud Computer was designed from the ground up to be a rack-scale cloud computing powerhouse, and so it’s optimized for exactly that task. Hardware + Software designed together By designing the hardware and software together, we can make hardware choices like more intelligent DC-DC power converters that can provide rich telemetry to our control plane, enabling future feature enhancements such as dynamic power capping and efficiency-based workload placement that are impossible with legacy servers and software systems. Learn more about Oxide’s intelligent Power Shelf Controller The Bottom Line: Customers and the Environment Both Benefit Reducing data center power demands and achieving more useful computing per kilowatt requires fundamentally rethinking traditional data center utilization and compute design. At Oxide, we’ve proven that dramatic efficiency gains are possible when you rethink the computer at rack-scale with hardware and software designed thoughtfully and rigorously together. Ready to learn how your organization can achieve these results? Schedule time with our team here. Together, we can reclaim on-premises computing efficiency to achieve both business and sustainability goals.
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Download Now View on pouet.net Intro In the late 80s, I spent an embarrassing number of hours hunched over my ZX Spectrum, typing in Sinclair BASIC programs and rudimentary assembler routines copied from magazines, trying to re-create the Amiga crack intros I’d seen round at a friend’s house. Obviously, they never came even slightly close - but now, many decades later, I’ve finally managed it! I’m now the proud author of a hand-rolled retro demoscene intro that runs on a stock 128Kb Spectrum. It features all those late 80s tropes: A smooth scrolltext (with ‘leet custom fonts!), a three-channel AY soundtrack, bouncing VU meters and the essential parallax starfield. It’s currently 10287 bytes of code, or 19552 bytes as a complete tape image - which, given I’ve been working on this since December 13th last year, means my average rate of code-production is a paltry ~ 455 bytes per week! This blog post is a technical overview of how I got there, some cool tricks I picked up, and everything I had to learn (and re-learn) about the Speccy and Z80 assembly along the way. It simultaneously rates as one of my favourite side-projects ever, and also the one that most often nearly triggered a foot put through my monitor in frustration. I’ll reflect on all that at the end, but for now if you just want to see the finished product, the download button is at the top of the article and the included .tap cassette tape image should load into any emulator. There’s also a YouTube capture, links to the production on pouet.net, and you can run it from within a web browser by visiting my TNFS site portal - check option 4 for recent uploads. Be Kind, Rewind But let’s skip back briefly to the late 80s. Coming from the world of an 8-bit, cassette tape loading computer, seeing an Amiga for the first time was like encountering something from outer space. Like everyone who saw one back in the day, I was blown away by the amazing graphics and sound on display, not to mention the library of ground-breaking games. But I found myself even more captivated by the mysterious (and totally badass) “intros” displayed at the beginning of pirated games. Created by the software piracy groups that had cracked the copy protection and distributed the floppy-disk based games, they were mini works of art in their own right - music, graphics and usually some cool-looking effect to show off the group’s prowess. There’s a great collection of these intros (or “cracktros”) archived on YouTube. Watch a few of those videos and you’ll quickly notice the “design” tropes that almost every cracktro shares: a cool, edgy logo at the top of the screen (bonus points if it’s dripping blood or in any way “metal”), some boastful text displayed on top of an effect of some sort - usually a scrolling parallax starfield, or rotating 3d object - and a further scroll-text full of shout outs, greetings to fellow pseudonymous crackers and adverts for illegal BBS systems galore. Needless to say, to a kid in the 80s/early 90s this was possibly the coolest thing ever. I thought this one was the absolute bomb when I first saw it. Sine-scroller, pirate BBS adverts, cool logo with a sword - and of course, a starfield. There’s something for everyone here. The music from this is burned into my brain. I think pretty much everyone of my classmates knew this intro given the popularity of Lemmings in the early 90s. Skid Row as a group are still active to this day and this is probably the quintessential Amiga cracktro of the period. Endless Piracy. Edgy. Another cool logo, sine-wave scroller, starfield and boasting text. The classics never go out of style. Another great combination of all the essential ingredients. Cool logo, even cooler text font, scrolling starfield and a scroll-text running along the bottom. Vintage stuff. Logo. Text. Scroller. But no starfield - otherwise a solid effort from Anthrox here :) The demoscene grew out of these intros. The cracking eventually faded into the background, and coders, “graphicians” and musicians all contributed to feature-length productions that showcased their abilities, competed with other groups and pushed the machine to its limits. In amazing feats of ingenuity and pure “code as an art form”, the scene lives on today, with groups producing breathtaking productions like this and this - bear in mind, both of those are running on a 7Mhz home computer equipped with a floppy disk, 1Mb of memory and a sound chip from 1985. But much as I admire the sheer skill and dedication that takes, it’s the early “single screen” scrolly-text-and-starfield cracktros I’ve always found captivating. They took on a sort of mystical quality for me, hinting at a scene and a culture I could only ever experience from the outside - which is exactly why I spent all those hours in Sinclair BASIC, trying in vain to re-create them, and dreaming of the day I’d eventually have an Amiga of my own. The Jump Back I eventually did trade up to a range of Amiga systems, joined a few “scene” groups myself and threw myself into a variety of activities until exams and the end of my teenage years beckoned. I dabbled with Z80 code back then, and at one point knew enough 68k assembly to bluff my way through - partly from the Amiga’s heyday, partly from a few “embedded systems” modules at University where I had to program a set of traffic lights or lift-controllers. Given there’s not much call for that sort of thing at my $DAYJOB, though, it had all pretty much faded from my memory. I have kept working on a bunch of projects in my spare time, and one of my favourites is my TNFS site - sort of an old-school BBS system or interactive “website” for the Spectrum, which grew out of a fun experiment to see how far I could push Sinclair BASIC. It relies on a modern network card fitted to the Spectrum, which is how I came to be chatting to “Desertkun”, another TNFS-protocol enthusiast. He’s now producing a great new WiFi network card for the Speccy, and was kind enough to send me a few of the prototypes to test out for him. I was massively inspired by his hardware and low-level coding chops, and during one of our video calls where we’d been comparing our development setups, he asked why I didn’t write any Z80 assembly myself. A throw-away comment, but the challenge was set! Now, I couldn’t face re-writing the whole site in asm, but I figured I could produce a self-contained intro to promote it in the style of the early “BBStros”, and finally be one of the cool kids with a scene production of my own :) I mean, how hard could it be ? (ooooh - foreshadowing!) Dev Environment My development environment through this was pretty straightforward, and is the same stack I use for developing my TNFS site. I just used a Makefile-driven build system which ran my code through the Pasmo assembler, my fork of zmakebas to build BASIC files, and the FUSE emulator for testing. For final testing on the real hardware, I uploaded my .tap files to my local TNFS server where I could run them on my +3. A few additional tools I have to call out because they ended up making a big difference - one is the amazing web-based “asm-editor” I discovered while looking up Z80 instructions. Not only does this site have a great reference of all the Z80 instructions, but it also has an editor where you can run example code and see how the memory and/or various registers change state. Take for example, the djnz instruction - you can build it and step through the example loop construct one instruction at a time. Or try my example of an add instruction in the screenshot to see how the carry flag works when a bit gets shifted out of a register. Although it uses a slightly different syntax to Pasmo (so I couldn’t drop my code directly in it), it massively helped when manually stepping through things. And lastly, probably the most significant debugging tools I used on this project - a notepad and pen, and my two dogs (say “Hi!” to Biscuit & Pebble…) I’ll write some more about this in the wrap-up, but this really was a highly unusual project for me, coming from decades of much higher-level languages and constructs. Most of my z80 code I only ever really understood after drawing out the bytes and bitmasks, keeping a table of register flags and drawing chunks of screen memory out by hand. And I found my evening walks with the two dogs provided ideal rubber duck exercises, although I’m not sure what they both made of my protracted mutterings about the hl register pair. Either way, debugging-by-dog is highly recommended! The Starting Point So, let’s get started. I followed a great “Hello, world!” example from futurice.com to validate my build environment. Beyond that, the first thing I wanted to do was load in my logo and background image I’d use as a “stage” for the remainder of the planned intro. I wasn’t really sure what I was going to do at this point, just that I wanted my logo at the top, and a scrolltext along the bottom row of the screen. As my TNFS site header already looked kinda demoscene-y, I made a quick edit putting in place two blue guide-bars inside which I’d put further content. Memory map courtesy of breakintoprogram.co.uk A Spectrum SCREEN$ file (usually displayed as loading screens) is just a dump of screen memory, starting from byte 16384, and running for 6912 bytes. The weird layout of this is very relevant later, but in order to display it all you need to do is load your file into that memory location. After a few hour’s work of reviewing Speccy internals and following various guides, I had a very simple starting point for my demo that served as the basis for everything else that came after. org $8000 screen EQU $4000 ; address of the first byte of screen memory, 16384 in dec scrlen EQU 6912 ; total length of the screen memory inc. attributes ula EQU $FE ; I/O port for the ULA to control the border black EQU 0 ; Spectrum colour number, the exact same ones BASIC uses start: ld a,black ; Set the border colour to black using the ULA out (ula),a ; Copy my logo header picture to screen memory ld hl,header ; HL = location of my screen file in this code ld de,screen ; DE = start of screen memory ld bc,scrlen ; BC = 6912 bytes to copy ldir ; block copy, see https://jnz.dk/z80/ldir.html ; busy loop - rest of intro goes here :P hold: halt ; sleep until the next interrupt (1/50 second) jr hold ; then jump back and sleep again, for ever header: incbin "assets/header.scr" ; my logo header/background end start Not much to look at now, but this simple starting point introduced me to important concepts like interfacing with the Spectrum’s hardware (ULA chip to start with, and AY sound chip later) via the out instruction, how to pull in binary files using Pasmo’s INCBIN directive, using the Z80’s block copy ldir instruction, the use of register pairs for 16-bit addressing, and simple branching to labels. Hello World The next step was to print something on the screen and explore some of the Speccy’s built-in ROM routines, which are somewhat analagous to syscalls on modern operating systems. There are plenty of disassemblies and guides to the Spectrum ROM available on the internet, one of the best commented and linked one is at https://skoolkid.github.io/rom/. Using this as a reference alongside the various “Hello, world!” tutorials showed me how this sort of thing is built up: at EQU 22 ; "at" control character used to position the cursor row EQU 11 ; coordinates where to print the message col EQU 9 prstring EQU $203C ; where the pr_string routine lives in ROM ld de,msg ; DE = address of the first character ld bc,msglen ; BC = how many characters to print call prstring ; print the lot ; busy loop is the same... msg: db at,row,col ; equivalent of "PRINT AT 11,9" in BASIC db "Hello, world!" msglen EQU $-msg ; 16 bytes in all, pasmo shortcut, $=program counter I ended up mostly not using the ROM routines in my code as they dragged in all sorts of things I didn’t need, but it was massively useful to understand how they worked as they introduced me to yet more commonly-used constructs. For example, the PR_STRING routine defined here shows how you can build a loop over each character. If you’re just starting out, I highly recommend going over the 8 lines in that routine with a notepad and pen, working out the contents of the registers and following the loop constructs. I also made a version of it in asm-editor you can try. If you click that link, you’ll see a version of the code loaded into the web editor. Click “Build”, and then step through the code using the “Step” button - although no text will be actually displayed (I skipped over the call to the Spectrum ROM “restart” vector that does this), you’ll see the various states of the registers and for example the BC register counting down as each byte of the string is processed. Adding Some Style Problem is, the Speccy’s built-in font is not exactly dripping with demoscene credibility. I wanted to use some stylish fonts and this turned out to be super easy - a quick search turned up Jim Blimey’s awesome font collection, which included a ready-to-use set of assembler files and some instructions which soon led me to these additions in my code: ; CHARS is the address the ROM's printing routine reads to find the font. ; Picking our own font is simply a matter of over-writing this chars EQU $5C36 ; from Jim's docs - POKE 23607=5C36 in hex ld hl,myfont-256 ; HL = font address - 256 as per docs ld (chars),hl ; from now on the ROM draws with it! ; rest of code is the same myfont: include "textfont.asm" ; "Cartoon" font from jimblimey.com There we go! Now that’s looking a little more elite. Sorry, I mean 31337. Strap in folks, we’re leaving lamer city… So at this point, a month or so in to my dabblings and I’d started to get a reasonable understanding of common idioms and was starting to feel like this was a project that might actually go somewhere. The problem started when I moved on to trying to implement actual demo effects: It became very apparent, very quickly, just how much I didn’t know about how this all worked. Not to mention the fact that at this level, you’re really closely exposed to the physical hardware intricacies, including the design decisions and trade-offs that the hardware designers had to make when working with the extremely limited specs of the early 1980s. Cursed Screen Layout The first such problem - and the cause of probably 90% of my pain - is the Speccy’s extremely weird screen layout. Rather than standard bitmapped display you might expect on more modern hardware, it is instead split into 3 sections, each with a set of interleaved rows (so if you keep adding 1 to a screen address, eventually instead of reaching the next row, you’ll instead end up 8 rows down, and so on until you hit the bottom of the section and then loop back to the row underneath where you started!) followed by a block of “attribute” bytes which determine the colours of each 8x8 block. The attribute blocks are the reason why each 8x8 character cell can only have two colours (a PAPER and INK attribute) which led to the garish “colour-clash” of spectrum games and distinctive style where artists try to keep inside 8x8 blocks as much as possible. But it was the layout of the bitmap portion that is such a mind twister. Download the video You can see this illustrated whenever a game reads in a loading screen from tape. You can see each section built up with the interleaved rows one at a time, and then finally the colour and other attributes (like flashing ). There’s a lot of detail at the fantastic Break Into Program site. In the defense of the designers, they were working with extremely limited hardware and I don’t think the Speccy was ever imagined as a games machine. When you start shuffling bytes around, you realise that this approach is really optimised for displaying text which is neatly arranged into 8x8 character boundaries. For example, using this “scrambled” bit order, if you have a screen address in the hl register pair, you can quickly get to the next pixel line of a given address by simply incrementing the “high” byte. There’s a bunch of other “cheap moves” you can make by simply shifting bits around: Move Instruction Right 8 pixels inc l Left 8 pixels dec l Down 1 pixel line inc h Up 1 pixel line dec h Down 1 character row add 32 to l It was a reasonable choice for a machine that would probably spend a lot of it’s time displaying BASIC program listings - it’s only when you start trying to write demo or sprite routines that it starts to feel really weird. This also means you’ll pretty quickly need a routine to convert X,Y addresses to the relevant memory addresses. Again, L Break Into Program has a useful routine and if you disassemble more or less any spectrum game or demo, you’ll find a version of this procedure somewhere. And yes, this all became horribly relevant later on… The Scroller Download the video Admittedly, not the most interesting demonstration - but this was the first time I had made something move on the Spectrum’s screen with assembly! I watched this with pride more times than I care to admit :) I had a snazzy logo and “Hello World” text, but that doesn’t make for a very interesting intro! The first effect I wanted was the scrolltext - without that, it’s not really an intro. Now, the Amiga had all kinds of hardware sprites, blitter operations, custom chips but the Spectrum had none of that. I was going to have to work out how to do things the hard way - “banging on the metal”, literally by shifting bits around the screen memory by hand and having the CPU do all the work. This is where understanding the Speccy’s weird screen and character cell layout is so important. It turns out there’s a neat trick as long as I stay inside one character row - there’s a RL instruction, which takes a byte and “rotates” it left. It inserts whatever is in the carry flag into the rightmost bit, and whatever gets shifted out ends up in the carry bit again. That means if you string a bunch of them together, you can move a set of pixels across the screen - the moment they “fall off” one character cell, they end up in the carry flag and then the next rl instruction inserts them at the beginning of the next character cell to the left. Repeat 32 times, and you’ve just moved a pixel (or set of pixels) across a line of the screen: linestart EQU $4880 ; leftmost byte of the line 12 rows down lineend EQU linestart+31 ; rightmost byte column ($489F) linelen EQU 32 ; one whole line is 32 bytes (character cells) across dot EQU %00000001 ; the dot "shape", just one pixel lit at the far right end newdot: ld a,dot ; load the dot shape (only rightmost pixel lit) into a ld (lineend),a ; store it in the rightmost byte of the line, pixel is now lit frame: halt ; wait for the next frame, otherwise it whizzes across too fast to see ld hl,lineend ; hl = last (rightmost) byte of the line ld b,linelen ; loop counter, 32 bytes to work through or a ; trick to clear the carry flag, or against itself leaves a register ; unchanged but clears various bits including the carry flag ; see https://jnz.dk/z80/or_r.html shift: rl (hl) ; rotate this byte left (00000001 -> 00000010) dec hl ; point hl at the next byte to the left djnz shift ; loop construct: b=b-1 and then jump back to shift label until b=0 jr c,newdot ; now we've shifted the whole line, so if the carry flag is set now it means ; the dot has just left the screen, so we jump back to the start jr frame ; otherwise it is still somewhere on the screen, so keep shifting! Download the video Hell yeah. It’s almost a proper scrolltext now! Wrapping this in another loop that increments h each time (remember - that gets us moving down a scanline) gets us moving an entire character cell. Here you can see it moving an entire row of my “Hello world” message. There was however a lot more work needed to make a proper scrolltext, with each letter appearing smoothly. I started off by just printing an entire character at a time on the right-hand edge of the screen - it worked, but was pretty ugly as you saw each new character appear at once in the right-hand side of the screen, scrolling 8 pixels over and then the next character flashed up. Instead, I wanted to make each character appear pixel by pixel and that required a bit more bit juggling. The routine I ended up with effectively streams each character in, line by line, pixel by pixel using the font data directly instead of calling the ROM print character routine. It does this by looking up the ASCII code for a character, and then fetching the corresponding font representation into a 8-byte buffer, one byte for each line of data. The font data starts with the space character (character code 32), so a lookup is simply font code base address + (ascii code - 32) * 8 to get to the bits for that letter. Arranged into an 8x8 grid, the bits for the letter H in the font data look like this. For each row of bits, I shift the line left using a neat trick. The byte is loaded into the a register, and then by adding itself to itself - add a,a we shift the value left (in binary, multiplying by 2 moves everything over one bit) so that the pixel I want to draw ends up dropping into the carry flag. This is an idiomatic way of doing it in Z80 code as it’s faster and smaller than the sla instruction. And every cycle quickly adds up when you’re re-drawing 256 bytes every frame! The character buffer then looks like this, with the top line shifted. Now, with the hl register pair pointing at the correct location on the screen, I can then use the rl trick discussed above. This shifts a scanline from the bottom character row of the screen left by one pixel and draws my pixel in the rightmost position by moving it in from the carry flag. Looping 32 times over this moves the entire row by 1 pixel with my new pixel inserted at the right. I then repeat this step again using inc h to move down one scan line until the entire character column has been drawn. At this point, the character buffer looks like this, and all 8 lines of the bottom screen row have all been shifted left by one bit by looping over all 32 character columns. The whole thing then repeats another 7 times until the entire character has been smoothly scrolled onto the screen. So just to re-state this because I think it’s worth the emphasis - just to scroll a message across the bottom of the screen, we’re having to loop over and re-draw 256 pixels every frame! It shows how much faster assembly is than the BASIC interpreter built into the spectrum’s ROM. I found it amazing to see my code finally working and imagining all the bits flying around and registers flapping away. It really makes me appreciate just how much effort went into creating the games I played back then. Music The original Amiga module I converted. A proper 1980s ear-worm! Of course, any good intro needs some music. On the Amiga, the standard was the “tracker” module format, which has a long and involved history of different forks, versions and tweaks. A song is built up from a series of patterns, each made up of rows of instructions. Each instruction usually includes note or pitch information, which sample to play and various parameters such as volume, effects - or in the case of some instructions, which position in the song to jump to. In many ways, it’s almost like a programming language for music. Using ProTracker as an example, a typical note cell is 4 bytes, shown on-screen as something like C-2 01 C20. That breaks down into three fields: the note and octave (C-2), the sample number (01), and the effect and its parameter (C20 - in this case, “set the volume to $20”, which is half of the maximum $40). A close-up of Protracker playing a tune. Note the VUmeters - another classic demo effect I would pinch later on! For an impressive demonstration of what’s possible with a tracker and to see what the note data looks like on-screen, check out the work of h0ffman, and in particular his winning “Professional Tracker” entry from the Revision 2014 competition. He’s an undisputed master of the science (or art!) of tracking, and his “Secrets of Protracker” talk gives a great overview of what’s possible. The Amiga’s sound hardware far eclipsed anything else on the market at the time, and the ZX Spectrum is paltry by comparison. The original 48K models only offered a rudimentary “beeper”, but the later 128K models included a 3-channel AY-3-8912 sound chip. This was very popular in 8-bit micros of the time, and a more-or-less identical variant was also used in the Atari ST. While it only offers basic waveforms and sound processing, it does enable multi-channel “chip music”, and so it became the mainstay of the ZX Spectrum demoscene. It also spawned a variety of SoundTracker clones on the Spectrum itself, although most musicians these days prefer to work in modern tools like Vortex Tracker II, which runs natively under Windows. The Conversion Pex looking back on his demos - this starts at the point where he features my letter and plays a bit of my cover version! For my intro, I wanted to port an Amiga module - and I had the perfect one in mind. One of my favourite Amiga music disks was “Sounds Of Gnome”, released in 1989 by the Swedish duo “Mahoney & Kaktus”. Mahoney also wrote NoiseTracker, one of the first really widely used trackers on the Amiga, and the program that served as my teenage introduction to making computer music of my own. Back in 2018 I made a rock cover of one of the other tunes on that disk, and wrote to Mahoney (real name “Pex”) about it. He ended up showing my “music video” at a demo conference, which I am eternally grateful for! So it seemed only fitting that I mangle another song from that collection with a Spectrum conversion… Sorry, guys! I picked the track “Milkman” which was written by “Glue Master”, an associate of Mahoney’s who had a few of his tracks featured on the compilation. It’s an ideal track for converting: It’s short (only 7 patterns in total), most of those patterns share the same chord sequence, and it looked fairly easy to squeeze the original 4 channels down into the Spectrum’s 3. Plus, it’s an incredibly catchy tune and I knew it well - I’ve been listening to it for 35+ years and often jam along to it on guitar or bass. The conversion started off pretty easily: all I really had to do was copy the patterns note-for-note from the Amiga mod, which I had open in OpenMPT as my Windows tracker. Below is a session with both trackers open on the same pattern - the original Amiga mod on the left, and my 3-channel Spectrum conversion on the right. Note the 11.7 in the 3rd channel of the Spectrum version. This is a “pitch slide down” effect in Vortex Tracker syntax, which drops the pitch by about a quarter-tone. It’s repeated on the next line, so the overall effect is a slide down from the A# that leads in to the next bass note. The original Amiga mod does the same thing using its own syntax - those are the 202s you can see on the same notes, at the bottom of the 4th track. Using just a single “beep” sound for everything was enough to check everything was working, and after a few weeks of hacking on it and re-arranging things in the evenings, I had a basic version which sounded surprisingly good for a first draft: Download the MP3 instead. I have to give a special mention to this forum post which was a massive help getting me started. It’s probably the best introduction to Vortex Tracker I’ve found - many, many thanks to the original author for taking the time to write it all up! The real challenge was making it sound as close to the original as possible. That meant building up a library of better-sounding samples for the different parts, and making extensive use of Vortex Tracker’s “ornaments”. Vortex Tracker comes with a great selection of sounds, and fortunately I’m also a weirdo who likes to listen to chiptunes in the background while I work! So whenever I found something particularly enticing, I filed it away for later pilfering inspiration. A Vortex Tracker sample isn’t really a “sample” in the Amiga sense of a recorded sound - it’s a definition of how a note sounds, one line per frame. Each line can mix in a tone or the white noise generator (useful for snare effects and suchlike), along with various other parameters. Ornaments, on the other hand, give you extra control over what pitch a note plays - and this enables really useful tricks like “arpeggio chords”. For example, an ornament of 0,4 makes the channel switch rapidly (25 times a second) between the note being played and the one 4 semitones above it. It happens so quickly that it sounds much like two notes played at the same time, which means you can build up full-sounding triad chords using only two channels. Take the opening chord in my fully converted version, Cm: It plays C in the first channel and the minor 3rd (D#) in the second, then I apply an ornament to the second channel to bring it up 4 semitones to the 5th (G). That gives all three notes of the chord, while keeping the 3rd channel free for other parts. As well as making much more efficient use of the limited 3 channels, this also gives Spectrum music that characteristic “warbling” sound, which I find really appealing in a retro kind of way! Between tricks like this and samples that mix tones with white noise (to make a combined “bass-snare” sound, for example), I managed to condense the full track down to 3 channels. Many months later, I have to say I’m really pleased with the final result. Playback The original site that was home to Vortex Tracker, documentation and other resources appears to be offline at the moment. I managed to grab a copy of everything I needed from archive.org - you’ll want the PTxTools.7z file for the playback routines discussed here. The playback was simple in theory: As this overview notes, you basically just pull in the player routine, include your module file and call the playback routine once per frame in your main loop. The catch is, none of the source code versions supplied in the archive worked with my Pasmo assembler. Fortunately, there is a pre-compiled binary object shipped alongside the source (VTII10bG in the PTxTools/PT3Play directory). This just has to be loaded in at address $C000 - this cannot be changed, as it has lots of absolute addresses baked in. My code to handle module playback now looks something like this, with the binary module loaded in place: ; Define the start address of the player routine and functions we need player EQU $C000 ; hard-coded org address of binary player plinit EQU player+3 ; init function in docs, module address in hl plplay EQU player+5 ; play and move on one frame ; from the docs - this "analyzes PT3 module header and prepares ; corresponding note and volume tables" ld hl,moduleimg call plinit ; main loop hold: halt call plplay call scroll ; other effects / routines go here... jr hold moduleimg: incbin "assets/music.pt3" Starfield Download the video Well, that didn’t work as hoped. TNFStro - tortoise edition. This brings me to the main event. No self-respecting cracktro is complete without a starfield! My first, naive approach to the classic starfield effect was to scatter random stars across the screen, then move down each scan-line applying the same rl trick I’d used for the scroll-text. I figured I could get parallax by shifting each row a different amount: One pixel for the first row, two for the second, three for the third, then back to one again, all the way down the screen to give the impression of several “fields” of stars moving at different speeds. It turned out there were two major problems with that approach. Firstly, shifting an entire row smeared whatever else was on it along with the stars - which I’d expected, and had filed away as a problem for future me. The bigger issue was speed: by the time I’d finished the first three rows I’d already performed hundreds of shift operations, and it was nowhere near fast enough to fit inside a single frame. Everything crawled across the screen, and the music playback slowed down so much that you could actually hear the arpeggio ornaments warbling away as separate notes. Clearly I was going to have to keep track of the individual stars instead. I found this routine, which was more-or-less what I had in mind and started me off with the idea of a structure to hold the state of each star. It also uses a screen address lookup much like the one from “Break Into Program”. Download the video Dammit. Back with another funeral dirge rendition :( That got things moving, but the co-ordinate lookup and tracking proved expensive to do (it has to run for every star, every frame as well as keep track of the old position for erasing) and I’d been ignoring the bigger question how to display stuff on top of the starfield. My original idea was simply to draw the stars and then paint text over them each frame, which blew the frame budget just as comprehensively as my first attempt. If I wanted something more interesting than an empty starfield, I’d have to keep track of which cells were occupied by text and avoid drawing stars in them in the first place, rather than over-painting them every time. After lots of scribbling in my notepad and visualising rows of bits, I eventually solved both challenges by “cheating” fairly liberally. So now, I don’t generate a random starfield at all. Instead, I built a table of pre-calculated Y and X position pairs: stdata: defb 109, 25, 88,182, 42, 96, 155,226 defb 59,254, 137,169, 160, 84, 125,193 ; ... and so on, for 32 stars ... This saves faffing about with an RNG, and once I have a layout that looks good I know it’ll always look good. I can also “fudge” things and ensure no two stars share the same y co-ordinate which sidesteps a whole class of problems like stars sharing a scanline, and having to deal with them overtaking each other. The “random” layout is generated by a simple Ruby script: #!/usr/bin/env ruby PAIRS = 32 PER_LINE = 4 # pairs per line Y_RANGE = 40..175 # exclude rows taken up by my logo & bars X_RANGE = 0..255 raise "y range too small" if Y_RANGE.size < PAIRS # no duplicate y values ys = Y_RANGE.to_a.sample(PAIRS) pairs = ys.map { |y| [y, rand(X_RANGE)] } pairs.each_slice(PER_LINE) do |row| body = row.map { |y, x| format('%3d,%3d,', y, x) }.join(' ') puts "defb #{body.chomp(',')}" end When the routine initialises, I convert those co-ordinate pairs into a table that tracks the state of each star. So rather than storing a position and translating it to a screen address every frame, each of my star records now looks like this (offsets from the base address): STSCR EQU 0 ; screen address of the byte the star is in, e.g. $4123 STOCC EQU 2 ; a pointer to the "occupancy check" table cell STMASK EQU 4 ; the star's bit pattern, e.g. %00010000 STSTEP EQU 5 ; "speed" - num. of pixels this star travels per frame The key thing is that there are no X/Y co-ordinates at all. For each star I store the screen byte it sits in and the bit mask within that byte, so it’s already in the form the screen writes need. That means no address conversion per frame, just simple bit shifting and rotation. Moving a star is then dead simple. I rotate its mask left with rlca, and when the bit rotates out of bit 7, it lands back in bit 0 with the carry flag set. That’s the signal I need to move the star one character cell to the left, which is one of the “cheap moves” from earlier. Because I’m tracking which cell each star is in, the collision check comes almost for free. That’s what the second pointer is for: STOCC (Star Occupancy) moves in step with STSCR through a table holding one byte per character cell. The “typewriter” routine sets a byte to 1 for every cell containing a text character or the cursor, so checking whether a star is hidden behind text is a single or instruction. If the cell is occupied, I skip drawing the star but carry on rotating and stepping it along until it reaches a cell where it can be displayed: ld l,(ix+STOCC) ld h,(ix+STOCC+1) ld a,(hl) ; A = the occupancy check for this cell or a ; test A against zero jr nz,stmove ; it's occupied, so leave the screen alone Parallax is still handled by moving each star a different number of pixels per frame, but the cost is a lot lower this time as I’m only touching the cells the stars actually occupy, rather than every byte of every row. Download the video That’s looking more like it! The typewriter routine is a simple copy of the font data from memory, and is very cheap as we can use the “cheap moves” to quickly fetch the 8x8 block. I also skip drawing any space character so it leaves the “occupancy cell” unmarked. This means the stars keep drifting through the gaps in the text - you can see here the odd star passing in between the words. I switched to ALL CAPS writing for the final version which helps the effect even more as the font is quite blocky, so you don’t really notice stars skipping the spaces inside a glyph at all. Misc Notes A few odds and ends that didn’t warrant a section of their own… VU Meters Some sort of graphic display bouncing along with the audio playback was another common early demo trope. I did originally consider a real-time graphic equaliser, but that would have been far too complex, probably in terms of spare cycles per frame, and definitely in terms of my limited mental capacity at this point! So I settled for a simple set of bouncing meter bars instead. It’s worth a mention mostly because it gives me an excuse to link to the awesome chibiakumas website! I just love the late 90s web design on display - one can argue that readability and accessibility take a hit, but it’s just so much fun to encounter a site that still looks like this. It’s a clear labour of love and there’s a wealth of content there as well, if your eyeballs are up to it. Their guide on Making Sound with the AY-3-8910 was what showed me how to get the data I needed to draw the meter bars. The examples write a register number to $FFFD to select a register, and I realised that once a register is selected, I could use the in instruction to read its value back out instead of writing a new one. As the page says, R8, R9 and R10 hold the channel amplitudes, so they feed nicely into the height parameter for drawing a bar. Getting the amplitude for channel A is then as simple as: ld a,8 ; Channel A register call ayread ; ... rest of code here ... ayread: ld bc,$FFFD ; Register select port out (c),a in a,(c) ret Twinkle, Twinkle, Little Star This is a simple effect that makes the header logo a little more interesting. I’m not sure where I originally got the idea - I’ve definitely seen something like it on a few late 80s/early 90s demos, though. All I wanted was to pick random star dots in the logo background and animate them. Here’s the header image loaded in ZXPaintbrush with the character cell grid showing. By happy chance, there are four stars which each sit neatly inside a single character cell with enough surrounding space, so they can be used to give an animated “twinkle” effect by drawing a cross out from the centre point and back in again. These dots map to the following co-ordinates, which target the top scanline of each fully-grown star (two pixels up from the centre): twkdata: defb 1,5 ; char row 0, col 5, centre y=3 ink 5 defb 1,20 ; char row 0, col 20, centre y=3 ink 1 bright defb 26,7 ; char row 3, col 7, centre y=4 ink 4 defb 25,22 ; char row 3, col 22, centre y=3 ink 6 bright The “twinkle” routine itself is simple enough: it adds a pixel on either axis to grow the star, waits a few frames, then shrinks it back down again. The interesting bit was how I made the twinkle order pseudo-random. Remember that my starfield was entirely pre-calculated from a data table generated by a Ruby script, which meant I’d never actually needed a random number generator in assembly. From Jonathan Cauldwell’s “How To Write Spectrum Games” e-book, I found another great “hack” which simply walks through the start of the Spectrum’s ROM, picking out random-looking bytes as it goes. As he says, he uses it in most of his games, and it does the job in a really simple way - as long as you stay below the block of structured, repeating data that sits 8Kb into the ROM. twkrand: push hl ld hl,(twkseed) ld a,h and 31 ; keep it within the first 8k of ROM ld h,a ld a,(hl) ; the "random" byte inc hl ld (twkseed),hl pop hl ret Out Of Space About halfway through writing the intro, I hit a fairly predictable problem: I had run out of memory. In an attempt to keep everything self-contained in one block of code, I was pulling all of the assets (the screen background, the player binary, the music file etc.) into the program itself, and then using the ldir block copy instruction to move each one into its correct location. Since that meant effectively storing every block twice, and the player routine had a hard-coded start address of $C000, I quickly ran out of room and my code started crashing into the playback routine. The simplest option was to split things out into separate code blocks, load each one directly to the address it needed to live at, and wrap the lot in a multi-stage BASIC tape loader: 10 CLEAR 32767 20 BORDER 0: PAPER 0: INK 0: CLS 30 LOAD "" CODE 40 LOAD "" CODE 50 LOAD "" CODE 60 RANDOMIZE USR 32768 This loads the main program, then the player routine directly into $C000, and finally the background screen straight into screen memory. It does mean the background starts appearing before the demo has fully loaded, but as I imagine most people will be seeing this running in an emulator or on my TNFS site, it doesn’t really matter. Plus, at this point I was in danger of disappearing down yet more rabbit holes (I still really want to work out how to do multi-colour border effects!) and I’d never have got this thing released. The Zen Of Z80 This whole project is a really weird one to look back at. On the one hand, I’ve fulfilled a childhood ambition and have something I’m very proud of. It’s also pretty unusual these days to end up with a binary where you can say pretty much what every single byte is doing and the story of how it got there. But on the other hand - I now have an answer for why I don’t code in assembly: It’s because I value (what’s left) of my sanity! The thing is, in order to write code like this you have to start thinking like the machine itself. You have to visualise the registers and the status flags flapping away, graphics as lines of bits slotted into strange orders, loops and conditionals as binary logic and so on. Getting this close to the hardware definitely brought about a greater sense of attachment to the hardware of my childhood, and it’s easy to see why assembly coders and sceners get so passionate about it. That said, I’m in no hurry to start re-writing my body of work in assembly! The projects I really enjoy are those that give me an excuse to learn something for the sheer hell of it, and to slow down a little from the ever-increasing velocity and demands of the modern work world. Going back to Z80 code is probably about the furthest I could have taken this, short of going into hardware hacking. I found it at times an intriguing puzzle, often a frustrating exercise that nearly had me throwing in the towel at several stages. This project has certainly taken the longest to go from the “idea” stage of any given feature to any kind of meaningful output. True, I didn’t spend every day of the last year working on it - my actual coding time was probably only a few hours over a couple of evenings a week. But I’ve certainly been thinking about it and pondering it most days (as my dogs will attest). The biggest breakthroughs and “aha!” moments usually didn’t come from behind the keyboard; they came from scribbles in my notebook and thinking about processor states while doing something unrelated. It has however given me massive appreciation and respect for the coders who pull this stuff off and make it look easy. And that goes double for those kids and bedroom coding superstars who managed all of this back in the 80s, and had to work it all out by experiment themselves. I only managed to get this far because of numerous books, online tutorials, GitHub repositories with sample code, YouTube videos… I can’t imagine how much longer this would have all taken me if the only resources I had were my Spectrum, a cassette tape recorder and a notepad. So, as I draw a line under this project - for now! - I raise a glass, and in the words of h0ffman: “Shout out to the hackers, graphicians and protrackers.”
A decade ago, a little bit of history was made. I didn't realize it, but a colleague made a great point, one of those real mind-changing points that seem too obvious to admit same-day. But, the next day, calver.org was born. At the time my team maintained the Python infrastructure for eBay and PayPal, and we were stuck deciding whether we were really ready for a "major" 1.0 release. Semantic Versioning was the only game in town and "major" means "big", right?! Thankfully, a wiser colleague mentioned: Ubuntu and Twisted don't struggle with version number debates. They slap a date on it and keep shipping. In fact, their date-based versions were even better because you always knew where it stood, in terms of updatedness and support. The only problem is that no one really knew about it. Somehow, this problem solving versioning alternative, arguably as old as history itself, had gone nameless for millenia, conspiring to make me feel foolish in an office meeting. Never again! Ten years of adoption Fast forward 10 years, we've seen CalVer adopted by Apple, Nvidia, JetBrains, and countless others. (We have a timeline!) The site may have more inbound links than any other project of mine. Apple made the biggest jump, at WWDC 2025: iOS went from 18 to 26 macOS from 15 to 26 watchOS from 11 to 26 and visionOS from 2 to 26 All landing on one, consistent number like a car's model year. I still remember the texts from the Venn diagram fanbase of my friends who love Apple and reasonable versioning. No such texts from when NVIDIA announced calendar versions across the GPU Operator, RAPIDS, and its monthly NGC containers, but still very cool. Open source, too: Home Assistant, pip, CockroachDB, and yt-dlp all ship on dates, with plenty more on the users page. The conversation even reached the language core; PEP 2026 proposed versioning CPython as 3.YY, and it almost happened, too. And it's never too late, time marches on! Fixing the notation But I don't think I got every detail right from day 1. That's the main motivator for CalVer 26. It's high time to start righting a couple idiosyncratic token design choices, starting with some additions: Meaning Before 26.0 26.0 Full year YYYY YYYY Short year (6, 16) YY YY Zero-padded year (06, 16) 0Y 0Y Short month (1 ... 12) MM M Zero-padded month (01 ... 12) 0M 0M Short week (1 ... 52) WW W Zero-padded week (01 ... 52) 0W 0W Short day (1 ... 31) DD D Zero-padded day (01 ... 31) 0D 0D Seeing double First, the doubled letters. From the first version (16.6), MM and DD meant the unpadded month and day, which reads backwards to anyone who knows date formats (ISO 8601's YYYY-MM-DD, Java, moment.js, day.js), as some community members correctly pointed out. I was ready to flip them, until I checked what people actually use: most projects with a YY.MM.MICRO badge (conda, Twisted, Ansible's tooling) don't pad, and more than a dozen other version management tools (like bumpver and bump-my-version) implement the old meaning. So, it's too late to flip MM's meaning. Instead, 26.0 deprecates it and offers a more explicit and hopefully clearer option: M is the short month, 0M the padded one, and MM is a technically-retired synonym for M. In case you're wondering, the explicit 0M was me being overinspired by Ubuntu's approach, perhaps: 6.06 pads its month but not its year, and YY.0M says exactly that. To pad or not to pad I think it's worth a detour into why padding is even a thing anyways. It's become important now that new ecosystems have emerged that enforced SemVer formatting semantics, and I wanted clear guidance about on the spec site. SemVer forbids leading zeros outright, so Cargo rejects 26.04.0 and Go modules reject v26.04.0. Even Python's packaging spec normalizes leading zeros away, so you can tag 2026.08.19 if you want, but PyPI will still show 2026.8.19. NVIDIA's GPU Operator docs put it this way: "Zero padding is omitted for month to be still compatible with semantic versioning." CalVer was always intended to drop in where SemVer was used. So 26.0 recommends unpadded (YYYY.M.D) as a sane "pure" default for software libraries. But libraries are not the only objects of versioning schemes. The exception is a version that becomes a filename, an image tag, or an object-store key that gets listed lexically. There, padding keeps 26.10 sorted after 26.09, which is why Ubuntu, NixOS, and NVIDIA's own NGC containers pad. More evidence of teams designing their versions. We love to see it. Our FAQ has a longer discussion of the padding issue, as well. Optional segments There was never any rule against them, but 26.0 makes optional trailing segments more explicit with square brackets. Now, yt-dlp's scheme can finally be written down: YYYY.0M.0D[.MICRO]. For the CalVer badges I could find on GitHub, they all stay valid for now. I've got a note on the deprecated spellings and a new copy-paste badge section for new ones. What else is new? It's always a great time to add more citations to the site. A spec changelog; the spec now versions itself: 16.6, 19.7, 26.0. A FAQ: breaking changes, same-day releases, and padding. The users page, rebuilt by category, with past users of note (schemes change; that's fine) and tooling. Case studies: Apple and NVIDIA in, yt-dlp replacing youtube-dl. Much of the thinking behind these changes happened in the GitHub issue tracker over the years, and 19 or so issues close with this release. That's where ideas for CalVer should go, so by all means, open an issue, and we'll get it sorted! In due time, of course. In closing, I can't believe I still love belaboring these numbers so much. Thanks to all (but especially Mark, Glyph, Hugo, issue reporters, translators, and maintainers) for the discussion, and ultimately making the most timely versioning system a timeless classic. See also 2016 announcement Designing a version My Yap on Why CalVer beats Semver
Four sincere attempts at OKRs, four failures, and every time: "you didn't do it right." Maybe the framework doesn't fit you -- so how do you find one that does?
Multiple concurrent writers. Multiple processes. Same SQLite. No modifications.
Brilliant jerks, ZIRP-era managers, and how psychological safety lost the plot. Part 3 of my conversation with Dr. Cat Hicks.
