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I learned how to swim at the age of 26. Or rather, I'm still learning. In my last lesson, I managed to swim 50 meters without using any support (and I didn't drown, lol). In the lesson before that, I got dizzy, my leg cramped three times, and I had swallowed half the pool. (you could see water draining) So today, I can't quite say, "I know how to swim now." But I also can't say, "I don't know how to swim." I'm learning how to swim at 26. And I have a few observations about it. First of all, there are a lot of children at the pool. A lot. And they're incredibly good at swimming. The first thing that happens when you start learning to swim as an adult is that, while you're desperately struggling around trying not to drown and taking huge breaths that somehow end up with you swallowing the entire pool, tiny little kids are happily swimming right beside you. It's an incredibly humbling sight. It strips away the ego you've built up over the years and the confidence that comes from being able to handle most adult tasks with ease, and suddenly you realize you've taken on something you know absolutely nothing about. Something that even children are better at than you. Fortunately, dealing with that part wasn't very difficult for me. One of the best skills I've ever developed in life has been being able to say, "I don't know," and accepting that I don't know. So accepting my lack of knowledge & skill came quite easily. The next challenge was digesting all the fear I had accumulated over the years. In the very first lesson, I was supposed to swim about 25 meters using a kickboard and fins. Instead, the moment my feet left the ground, I started flailing, struggling, and trying not to drown even though my head was above the water the whole time. My first few lessons were spent simply trying to get into a horizontal position in the water. Up until that point, it was all just fear of the water. My instructor literally forced me to the bottom of the pool, and I saw that I could come back up. Once I realized, somehow, that nobody was going to let me drown in that pool, I started being a little less afraid. Even then, it took me getting three leg cramps just to make it 25 meters with a kickboard. I was tensing my body far more than necessary and pushing myself to an absurd degree. By the end of the first month, my only plan was to quit. To justify it, I had convinced myself of all sorts of reasons: that my instructor wasn't attentive enough, that I wouldn't have time for swimming lessons, that maybe swimming just wasn't for me. I kept going through that first month simply because I had already paid for it (while also looking for every possible excuse to conveniently skip lessons whenever I could), but watching the people who had started at the same time with me improve while I was still struggling so much made me feel awful. One day, about an hour before class, I was sitting on the floor of my bedroom thinking about why things were going this way, why I couldn't do it, why I would never be able to do it. My spouse came in and told me to get ready for the pool. I told him I couldn't go. He said, "I don't think you're afraid of the water. I think you're afraid of failing." I cried a lot that day. I didn't fully understand what I was feeling, but I was certain I wouldn't be able to get into the water. Ever since the beginning, every single day I had been trembling as I walked through the door, making self-deprecating jokes and coming up with excuses to turn back, but that day I couldn't even bring myself to leave the house. I wasn't confronting my fear of water anymore. I was confronting my fear of failure. After taking lessons, trying at least five or six times, I still felt like I was exactly where I had started. And I felt like I would never get past that point. The next day, before class, I went back and read some of my journal entries. I remembered how, during my first lessons, I couldn't even get into the water with a kickboard, and I remembered the cramps. At the same time, I realized something: every single day I chose to go swimming, I ended up swimming better than the version of me where I didn't go at all. That day, when I got into the water, my instructor happened to be busy with other students, so he left me alone for a while. Instead of following memorized instructions like a robot, I tried to understand how the water actually worked. I experimented to see what happens when I did different things, and by the end of that lesson I realized I could stay afloat on my own. At the end of class, I told my instructor that my learning style was to repeat something until I truly understood the dynamics behind it. I needed to discover every possible outcome of a movement through trial and error. I started feeling a little better. In the next lesson, I practiced not next to the wall but between two lanes. My instructor believed I could do it now. Even though I resisted a lot, he refused to change his mind, and I tried to stay afloat between the lanes, with no wall to hold onto. On my way to the lesson after that lane incident, I noticed my feet wanting to turn back again. I can analyze my own pattern now. Whenever there's a new challenge, an unfamiliar path, taking that first step doesn't come easily to me. When I had finally gotten used to swimming safely alongside the wall, knowing that the next lesson would be between the lanes scared me. Then I got used to swimming between the lanes, but now I had to let go of my kickboard. After swimming without the kickboard for the first time, I once again didn't want to go to the next lesson. Then I learned to let go of the kickboard. Next came getting rid of the fins. We had a lesson where I swam 50 meters without fins, without a kickboard, without any kind of support. And yet I still didn't want to go to the next lesson. Even though I had done it, even though I had concrete proof that I could do it, the idea of getting into the water without fins in the next lesson terrified me because I still wasn't confident in my abilities and I didn't know whether I would fail or not. Once again, I couldn't bring myself to go. That's where I am now. I convince myself to go to class (most of the time by telling myself not to waste the money I've already paid), and I'm incredibly happy whenever I manage to do something I couldn't do before. Just being in the water gives me enough courage to attempt something I've never done before, and I finish the lesson. Before the next lesson, I'm afraid again because I know I'll be facing something new. I skip lessons with all kinds of excuses until, the next day, I convince myself all over again and see that I was actually capable of doing the very thing I was afraid of. I have to remind myself of this pattern often. That many of the situations I feared so much, the ones that sent me into anxiety and fear spirals, eventually turned into skills I genuinely enjoy, and that I have more than one example of this happening. Before my next swimming lesson, I'll read this piece again. Every time I try something for the first time and don't become great at it within ten minutes, I'll remember what learning to swim felt like. There is nothing quite as satisfying as learning something new, especially something you're bad at, and watching yourself slowly become good at it. These are some of the moments that make you feel like you're truly living, like you're expanding your own limits with your own hands. I can't wait for swimming in the open sea and to exploring the open sea of possibilities by taking on new things I'm bad at. Thanks for reading. If you have any feedback or would like to discuss further, I would be happy to hear from you. twitter | [email protected]
Exactly a year ago today, I changed something about myself that had been part of my life for ten years. What that "thing" is won’t be mentioned here, so as not to take the subject out of context, but I can tell you a few things about it. Because it had persisted for a decade, it had become more than a habit, it was an identity marker. Whether people knew me well or not, they could easily list "being that thing" or "having that thing" among my traits. Among my friends, family, and relatives, there were many who were deeply attached to this version of me. It felt as if their entire connection to me depended on my possession of that thing. I started thinking about changing this thing a long time ago. About 4 or 5 years ago. In other words, half the time I spent having that thing was spent imagining letting it go. Throughout that entire period, I believed it was absolutely impossible for me to change it. Knowing I couldn't change it and continuing to live that way only brought me pain. Though I tried to ignore it most of the time, it was with me at almost every moment of my life, and the discomfort it created caused me to shy away from many possibilities in life. Many. One day, I was crying like a regular tuesday night, I decided to change it. And I changed it right then and there. I went for a brisk walk, and by the time I came home, I was someone who had changed that thing. It was over. Now, the next step was for everyone around me to find out that I had changed it. Because until everyone knew, I wouldn't be fully changed. As I said at the beginning, there were people among my loved ones who were truly attached to me being "that thing"; even though my changing it had no direct impact on their lives, and even though it was entirely, solely, and only about me. There were people who had nervous breakdowns, people who cut off contact with me, people who were shocked, people who were overjoyed, and people who made no comment at all. This process gave me a lot to think about how people become attached to versions of us that they find convenient for themselves I went to therapy for a while to decide if I should keep the change and how to do so. The discomfort of the change was so intense that I began to wonder if it would be worth it. It took several therapy sessions to figure out if I actually wanted to change the thing about myself. It felt as though the happiness this change would bring would never outweigh the discomfort it caused. I was very close to giving up. But whatever happened, I somehow endured. I am not exactly sure how that one year passed, but I'm glad I didn't back off. The people who matter most to me accepted this change. Our communication returned to normal in a few months. As for me, I often find myself sighing. Even though everything looks normal, I am still living with the inner ache of that change. I believe part of me, no matter how much I wanted the change, was somehow connected to that thing. Probably because it was an identity, a habit, something I lived with for 10 years. It is hard to let go such a thing. I have some people I cut out of my life so that they will never find out about the change and I will never have to put on an explanation. I am 26 years old, and I believe this is the first time I choose my own way of life even if it conflicts with everyone else's opinions about it. It took me five years to decide on a change. It took a single night to take action. And struggling with the discomfort of that change has taken about a year. About six months ago, I began to feel the sting of regret for not finding the courage sooner. Still the change reminds me of its presence from time to time, bringing back that familiar uneased state of mind, and I don’t know how much longer that will last. Yet, the moment I actually started to enjoy the change was the very next morning after that walk. When I thought beyond everything else and realized I had finally achieved something I’d spent years doubting and deeming impossible.. that excitement was priceless. I don’t know how much time must pass before the transition is complete and the act of changing finally leaves my daily thoughts. But in a way, I don’t want it to. Making this change was one of the most significant decisions of my life. Even with all the discomfort and the struggle, I wouldn't trade the excitement and fulfillment it brought me for a smoother, easier path. Thanks for reading. If you have any feedback or would like to discuss further, I would be happy to hear from you. twitter | [email protected] Previous
Most of the audience reading this post think of some random new programming tool dropped recently when the word library comes up. Let’s leave our déformation professionnelle in the door and think about the libraries. Book ones. This post is an ode to them. I am not sure if libraries work the same way everywhere around the world but in my country they are completely free, you can sit for hours, borrow books, again, for free. The idea of borrowing something from an institution without owing them anything in this time we’re living in amazes me. I mean who gives you free stuff (except free pain)? This fact itself is enough for me to think libraries are amazing. I consider myself a decent book reader and it’s been a long long time since I had to pay for a book. But this isn’t the only think I like about my libraries. So the story begins with me, a remote working software developer getting married to a remote working software developer. My husband and I are a newly wed couple with all the fun and silliness but life (work) gets in the way naturally. Traditional couples see each other a few hours every day, and usually spend the weekends together to make up the lost time. We don’t have the lost time. We’re together, always. Working in the same room (our home office) resting in the same room etc. and god, we annoy each other. Love only goes so far, folks. Love is great for your daily life, for your home. But what if your home is also your work? And what if your work needs some limits on the PDA? You can (ideally) leave your work stress and burden when you leave company building. However, when remote working, you’re not leaving work at all and even if unintentionally, that mood rubs off on your partner, who has the same tension from work. I’ve spent all of my teen years and a couple of my twenties in student dormitories which I had to share my room with at least 4 other girls. That fact alone justifies that I love and need my personal space and time in my home. And my partner also needs that, even if he doesn’t say so, I know he needs. And we respect each other on this and try to leave the house for a couple hours every now and then. Again, any traditional couple may not need this kind of arrangement, one or both of them having to leave for work, but we’re not like the other couples. It’s not always related to your partner / roommates / family. Even if you’re having enough personal space, enough distance from others, home office still can be life sucking. I’ve spared the biggest and prettiest room of my house as the home office. I’m talking about wall-size windows, glittering sea in front of me, big sky and trees. There is a real view I can’t describe enough. (It’s a house that’s a few decades old, and we are just tenants so don’t think too much of me lol) And I’ve decorated the office pretty nice, spaced, refreshing. Even with that perks, being at home all day just consumes my soul. I can't focus after a couple of hours. Especially if I haven’t left the house all day, rolling out of bed straight to the desk, it becomes too draining. I need the concept of leaving home for work, and I need the feeling of “arriving home”. Getting cozy again after a long day, hiding from darkness of the outside world (work) Being at home while working AND while resting, my brain just can’t switch off between work and rest, drawing a line between bad and good. I’ve talked about my feelings, but no need to mention here, you’ve probably read all about health and psychological problems that remote work causes. With all these said, it’s almost mandatory for me to adapt a hybrid work approach. You may think, just go back to the office. No, no. This is not an option. First I don’t even live in the same city with my office building. Even if I did, it’s too late for me to adapt to office work. My work life started remote, even my internship was remote. I don't have office experience. I don’t know what am I going to do if I have to work in an office job in the future. Leaving your warm bed, rising before the sun in the morning (and I’m a morning person believe it or not), getting ready, commuting, traffic, thinking about what to eat in the office, commuting again, leaving you no time to live your life.. No. I don’t want to think about that possibility. It’s not for me. Also having a home office is not bad at all. Somedays you just don’t want to leave the house, maybe you’re a bit sick, or just not feel like it. It’s good to have the option to stay in bed while working. In other words, stay in bed and get paid. I just need a context switch for a couple days in a week. So what to do? Go to nearest coffee shop. You’re lucky if they don’t play tasteless trendy music. You’re lucky if a waiter doesn’t keep asking if you need anything, isn’t intrusive, and doesn’t subtly let you know when it’s time to leave by checking on you constantly . You’re lucky if no teenagers talking loudly about their-whatever-teens-talk-about-these-days. Oh, by the way, pay a lot of money to be here and to drink a nice cup of burnt coffe. Working in the coffee shop might feel cool just for one day, just for the vibes. Not maintainable. Then rent an office or subscribe to a co-working space? What? I get paid to work, not to pay for it. And here comes the raison d’être of our ode, libraries. Go to your local library. Set up your working tools. That’s it. No one will talk to you, if you’re in a relatively small one, chances are no one will be there. Just you, the nice vintage smell of the books surrounding all over, and a nice vibe. You’re tired, want to take a break, you’ll walk around book shelves and you’ll see there are very odd books on very specific topics. Take it, or laugh at the title, free amusement. Share it on twitter, free likes. Find some hard-cover, old, brown page books. Smell them, feel good. Free joy. Get back to working. Stay focused, finish your tasks without your bed luring you to itself. No distractions, no funny businesses. I use a technique that maybe we can call laptop-driven-development: working until my laptop does not feel like it anymore. I don’t plug my laptop so my work has a natural deadline for the day. I need to stay focused and get things done, or I’m gonna have to get back home with leftover tasks. Fall is on the way, maybe it’s raining outside. With big windows all around you, overthink your life while waiting for the rain to stop before heading back home.. This is my call to all the remote workers or students or any other people staying home too much: Go to your local library, enjoy it, support it. Cherish it. Not just for working. Use it for thinking, for reconnecting, writing or creating. The library is a sanctuary where your mind slows down, even though the world outside keeps running. Maybe you’ve been postponing to think, to reflect, to spend time by yourself, like I did before I discovered my local library. You’ll find some kind of joy and productivity in there. We don’t have so many pure-good organizations in our world. We should appreciate them while we still have them. I’ll admit that this post can be a little biased, because my local library isn’t exactly a popular spot. Most of the time, I’m the only one in a room, and there are only 3–4 people in the rest of the library. It’s just a 20-minute walk from my home, so I get to walk my daily steps in on the way there and back. And some of the rooms look like this: Yes, I’m lucky on that. Yes, this is where I write this blog post. This post has been discussed on Hacker News, you can join the conversation there. Thanks for reading. If you have any feedback or would like to discuss further, I would be happy to hear from you. twitter | [email protected] Previous
know thyself There is a new lifestyle imposed on almost the entire world, willingly or unwillingly, perhaps by powerful people or by many small people that want to be powerful, which somehow affects all ordinary people: a consumption-oriented life. Fast consumption, constant consumption, more consumption. I don't have much to say about the "shopping" side of this consumption craze because it's a topic that's been around for many years, born out of -ism movements and studied numerous times through -ology disciplines. It has been the subject of public service announcements, romantic comedies, and personal development books. The public has been constantly educated about it for years. Two guys known as The Minimalists and some "smart" people like Marie Kondo made a fortune out of this movement. Personally, I believe I am a conscious consumer, and the shopping craze doesn't affect me much, so I want to look at the other, often-discussed side of the issue. The consumption I will discuss is digital content, information, and emotion/thought consumption. I know there are social science studies that delve into the intersections and background connections of all these consumptions, but as an ordinary person, I want to talk about the effects on my own life, particularly my professional development. Although it has been on my mind for a long time, I haven't been able to read a comprehensive book based on these studies (the reason being the vicious cycle based on this topic), but I have consumed plenty of content... I've watched various TED talks, several indie YouTuber videos with a wholesome background, selling personal development under the hood on their newly launched channels, and of course, read tweets... I've also had plenty of opportunities to observe myself. At this point I am convinced that fast consumption is harmful to the brain, mind, and soul. The main reason I pursue this topic is that, aside from all the side effects in personal life, it also prevents me from being better at my profession as a brain-worker as Jules Payot puts it. In disciplines like software engineering, constantly improving oneself and being in a state of continuous learning is an inevitable process. Even if you don't put in extra effort and just try to do your job, you have to learn a new concept or technology. If you do put in the extra effort, you become someone who does their job better. Since graduating from undergraduate studies (which marks exactly one year as I write this post), putting in extra effort has been my top priority. Working more, reading more, knowing more. In addition to technical studies, I also read about and received advice on soft skills related to "software crafting." One of my first mistakes, I think, was taking every kind of advice from everyone. Even if I didn't implement them directly, these pieces of advice took up space in my mind, and thinking "what if that's better" prevented me from putting any of them into practice. The problem with online advice is that the person writing the blog post is doing so entirely from their own perspective and lifestyle. They have no idea about you, and you have no idea about them. There's no guarantee that what works for them will work for you. Moreover, you don't get a chance to question causality, you just read the advice, consume it, and move on. It takes up space in your mind and on your to-do list, but you don't get a chance to internalize or filter this topic. You don't even realize that you should actually do so. One of the pieces of advice I took without realizing it was to systematize the mentioned studies, work regularly, and similar. Once that idea put in my mind, things became complicated for me. While working full-time, I had to balance my personal life and stick to the plan. No matter how much your willpower sticks to the plan, your health, developments in your life, and your brain, which sometimes refuses to accept more information, don't always stick to the plan. When this happens, it becomes difficult to establish the system I mentioned, and you start looking for more advice, reading more blogs. You find yourself in a quest for productivity, feeling productive because of the quest, but not really doing any productive work. Advice also has the effect of reducing creativity and problem-solving skills. When I have a problem, technical or other, the first thing I do is research the solution. As a result, I don't get enough chance to think about my problem, let alone produce a solution, and I don't fully understand the problem. I've "consumed" what I should do and how I should do it many times from different people. With all this information occupying my brain, I no longer had the energy and resources to produce a tangible output. Because of my profession, I like learning different concepts from different fields. I am particularly curious about the low-level infrastructures and systems behind high-level tools, and I am aware of the contribution of knowing these to doing my job well. However, because of the constant rush and haste imposed by social media in my life, I can't devote enough time to these resources. Because I am so used to seeing information, quickly taking it in, and moving on to another topic. Because the short content I constantly consume, whether written or visual, has made me accustomed to this. I want to know everything, immediately, quickly. Since this is not humanly possible, I end up doing nothing. I can't think long-term; I can't stop myself from thinking that working on a book for 6 months, doing its projects, is a huge waste of time for me, and because I already feel late, I find myself, yet again, in a cycle. When I'm focused solely on consuming, my ability to produce naturally decreases. I include speaking, being able to express oneself, and having a good command of words in this context. After knowing myself as someone who has always been good with words for years, seeing that I can't choose the right word when speaking, or that I can't convey the message or information I want to give more clearly and simply when writing, naturally bothers me. Although it is said that software development is an antisocial job, you constantly need to communicate with people, either in writing or verbally, and you need to express what you have done and what you will do well. I am approaching the point of losing this skill by consuming instead of producing. While all this disrupts progress and confuses my mind, I also have to deal with the physical and mental side effects of fast consumption. Difficulty concentrating, lack of focus, inability to understand what I read, stress, anxiety. I see these kinds of complaints from many people lately, and in my opinion, our biggest common ground is digital content consumption. The relativity of time is a reality I feel to the core while doom scrolling. Besides the lost time, there's the confusion after realizing it and putting the phone down, trying to get my dazed mind back to normal. And then, not finding anything to do, not being able to putting yourself together, and reaching for the phone again. Everyone has seen the articles about the brain's approach to social media content, which offers a quick, easily accessible way that makes you happy or, even if it doesn't make you happy, offers an escape from the thing that makes you unhappy. When you put these into words or write them down, it bothers you a lot, but I think knowing yourself is the most important thing to do before changing yourself. I know what I'm doing wrong, and now it's documented in front of me. I also know what I need to work on. We are talking about the harms, but I have always been fascinated by the opportunities the internet offers. Being able to communicate and chat with someone from anywhere in the world within seconds is an invaluable blessing. It just takes a little effort to filter to see and reach the right people's content. Otherwise, I don't think completely withdrawing would be very beneficial in my industry and the era I live in. I won't go against what I mentioned so I won't end this problem-filled post with advice or plans. That's why I started with the quote "know thyself." I just tried to see and make the problem tangible. I will stop researching what I can do for a while. First, I plan to clear my mind of clutter, quit this fast and excessive consumption habit I have acquired without realizing it, and then learn how to consume slowly and gradually. I have enough raw information to discover how to do all this myself; I will now give myself the opportunity to process it. This post has been discussed on Hacker News, you can join the conversation there. Thanks for reading. If you have any feedback or would like to discuss further, I would be happy to hear from you. twitter | [email protected] Next
More in technology
Sometimes it's easier to identify an IC with a microscope. While sorting a box of old ICs, CuriousMarc came across some Harris ICs labeled "F1-10-5", a mysterious part number that didn't show up in any databooks. Since unidentifiable ICs are useless, he gave me one to analyze. Conveniently, it was in a ceramic package, so I could open it up with a quick tap from a chisel. Under the microscope, the chip's most striking feature was a grid of square capacitors. With all those capacitors, I guessed that it was a switched-capacitor filter. The die provided another clue: the part number HF-10. With this information, we quickly found that the chip was Harris's version of the standard MF10 switched-capacitor filter chip.1 The Harris integrated circuit, labeled F1-10-5 (or maybe FI-10-5), with a 1985 date code. Photo courtesy of CuriousMarc. Switched-capacitor filters were a popular way to implement analog filters in the 1980s. Rapidly switching capacitors in and out of a circuit enabled the construction of single-chip filters that were easy to use and performed well. The MF10, introduced by National Semiconductor in 1981, provides two flexible filters on a chip; each filter acts as a low-pass filter, band-pass filter, or a high-pass filter. The filter's characteristics are simple to control with a few external resistors. The Harris HF-10 die under the microscope with the main functional blocks labeled. (Click for a larger image.) Since I had the chip under the microscope, I took the opportunity to analyze it more closely. The white lines are the metal wiring that connects the chip's circuitry. Under the metal layer are two layers of polysilicon (reddish) and the underlying silicon (gray). The top and bottom halves of the chip are mostly mirror images, corresponding to the chip's two filters. The distinctive reddish squares in the middle of the chip are 72 tiny capacitors, constructed from polysilicon. Above the capacitors, CMOS switches turn on and off at the clock frequency, switching capacitors in and out of the circuit. Each filter uses three operational amplifiers (op amps), outlined in red. At the right are the three outputs from the three op amps: high pass, band pass, and low pass. The control circuitry is on the left: clock level shifting, clock shaping, frequency ratio handling, startup circuitry, and current sinks to provide fixed currents to other parts of the chip. Around the edges of the silicon die, 20 hair-thin bond wires connect the die to its 20 external pins. The die has some interesting chip art: a Harris logo and an outline of Florida; Harris was headquartered in Melbourne, Florida. The initials on the die are presumably the engineers who designed the chip. Some interesting images from the die. Switched capacitor circuits The filter is based on switched-capacitor circuits. A switched capacitor can replace a resistor in certain circuits, as shown below. The switches are controlled by a clock signal; the switches alternately close in clock phase 1 and phase 2 (ϕ1 and ϕ2). In phase 1, the capacitor is charged to the input voltage. In phase 2, the capacitor passes charge to the output. By rapidly toggling the switches, charge is (almost) steadily passed to the output. The larger the capacitance, the more charge that is passed through. Likewise, a higher frequency passes more charge. It can be shown that the circuit matches a resistor with resistance of 1/(fC): a higher capacitance and frequency correspond to lower resistance. A switched capacitor can replace a resistor. Why would you replace a simple resistor with this complicated switching circuit? In an integrated circuit, resistors are inaccurate and inconveniently large, especially high-value resistors. Replacing a large resistor with a small capacitor saves space on the die. Moreover, it is easy to generate an extremely accurate clock frequency with an inexpensive quartz crystal, making the filter's frequency highly accurate. Finally, the equivalent resistance can be changed simply by changing the clock frequency, making it easy to tune or sweep the filter. On-chip capacitors are fairly inaccurate, with the capacitance typically varying by 20% from chip to chip due to variations in manufacturing conditions. However, this isn't a problem in the MF10 because the circuitry was designed to depend on the ratio between capacitances, which is stable. Specifically, the MF10 uses 72 identical square capacitors, which will have almost identical capacitances. Careful examination shows that some of the capacitors are separate, while others are connected in groups of 8 to form larger capacitors.2 This yields a highly accurate ratio of 8:1 between the grouped capacitors and the individual capacitors, even though the absolute capacitance will vary from chip to chip. Each capacitor is constructed from two layers of polysilicon,3 forming the plates of the capacitor, separated by a thin layer of insulating oxide that acts as the dielectric. I estimate that each capacitor square is 5 picofarads. The grid of capacitors in the MF10. I've added yellow lines to show how the capacitors are grouped. The switches are above and below the capacitors. This chip uses one more trick with switched capacitors: it inverts the voltage while acting as a resistor. In the switched-capacitor circuit below, there are four switches. The capacitor charges to the input voltage during phase 1, the same as before. But duing phase 2, note that the top plate of the capacitor is grounded, while the output comes from the bottom plate. If the capacitor was charged to, say, 1 volt, the top plate is 1 volt above the bottom plate. So if the top plate is grounded, then the bottom plate must be at -1 V. (This is the same idea as a charge pump.) This circuit turns out to yield a more accurate filter because some parasitic capacitances cancel out. By using four switches, the switched capacitor can invert the voltage. The op-amp integrator The heart of most analog circuits is the operational amplifier, or op-amp. An op-amp takes two inputs and amplifies the difference by many orders of magnitude. Normally, an op-amp is configured with negative feedback, which forces the two inputs to be essentially the same. Op-amps are useful not only for amplification, but for filtering, buffering, summing, and other tasks. A basic op-amp integrator. The filter chip uses op-amps as integrators, to integrate an input voltage over time. The circuit above shows a simple op-amp integrator. The input voltage produces a current that flows through the resistor and charges the capacitor, so the capacitor holds the integral of the input voltage over time. You might expect that the left side of the capacitor would become positive as it charges. However, the op-amp's feedback forces both inputs to ground, so instead the right side of the capacitor becomes negative. Thus, the output is the negative integral.4 The MF10 chip uses the circuit above, except the resistor is replaced with a switched capacitor. The capacitor across the op-amp is not switched, but consists of either 8 or 16 capacitors from the capacitor grid. The CMOS switches The CMOS switch is the technology that makes the switched-capacitor filter possible. A CMOS switch has a fairly low resistance (maybe tens of ohms) when closed and an enormously high resistance (hundreds of megohms) when open. This high resistance ensures that the charge doesn't leak out of the capacitors. A CMOS switch is constructed by combining an NMOS transistor and a PMOS transistor. The NMOS transistor and PMOS transistor are opposites. An NMOS transistor is good at pulling the output low, while a PMOS transistor is good at pulling the output high, so in combination they provide an effective switch. An NMOS transistor is turned on by a high voltage on the gate, while a PMOS transistor is turned on by a low voltage on the gate. Thus, a CMOS switch requires two control signals of opposite polarity, which is a minor inconvenience. A CMOS switch. The diagram above shows how a switch is implemented with an NMOS transistor and a PMOS transistor in parallel. When the control line is high, and the inverted control line is low, both transistors turn on, providing a path through the switch circuit. When the control line is low (and the inverted line high), the transistors turn off, opening the switch. The chip uses CMOS switches in pairs, with one switch on and the other off. This forms the equivalent of a toggle switch that connects either A or B to the output. This circuit is simply two CMOS switches, with separate control lines for each switch, as shown below. In the MF10, the switch toggles at the clock frequency. During one clock phase, the switch is connected to A, while the switch is connected to B during the other clock phase. The schematic on the right, below, is the same circuit, but reorganized to match the layout on the die. A double-throw CMOS switch. The photo below shows a CMOS switch on the die, constructed from two PMOS transistors and two NMOS transistors. The four control lines run horizontally in polysilicon, forming a transistor gate where they cross doped silicon. The upper PMOS and NMOS transistors are driven by the clock phase 1 (Φ1) signals, while the lower transistors are driven by the phase 2 signals. CMOS switches on the die. The metal layer was removed to show the transistors. One problem with switched-capacitor filters is that the clock can generate switching noise that appears in the chip's outputs. The MF10 uses several techniques to reduce clock noise. Each set of transistors is surrounded by two isolation rings: one positive and one negative. These block noise from traveling through the silicon substrate. Note that the rings have opposite polarity for the NMOS transistors and the PMOS transistors. The light tan region in the photo above is a second layer of polysilicon. This polysilicon is connected to ground, providing a shield layer over the switching circuits. For the photo above, I removed the metal layer with acid5 to make the transistors more visible. The photo below shows the original die, with the metal layer connecting the transistors. The small black circles are connections between the metal layer and silicon or polysilicon. The same CMOS switches, showing the metal layer. Putting it together: the state variable filter There are many ways of creating a filter. The MF10 chip uses a technique called the state variable filter, invented in 1967. This circuit acts as three filters, with high-pass, band-pass, and low-pass outputs. Moreover, the circuit is flexible since the frequency, the gain, and the filter quality (Q) can be varied independently. It uses three op-amps: one to sum signals and two for integration. By changing how the values are summed, the characteristics of the filters can be changed. The diagram below shows a simplified representation of a state variable filter. The mathematics behind a state variable filter is complicated, so I won't get into it. In short, the signal, the integral, and the double integral form the three state variables that define the state of the system. Simplified diagram of a state variable filter, with two integrators. Inspired by North Coast Synthesis. The block diagram below shows how the filter is represented in the MF10 datasheet.6 The diagram is similar to the diagram above, with three op-amps. However, the summing circuitry has been separated out. Moreover, the feedback paths are not shown explictly. Instead, resistors are connected between the chip's external pins (squares) to configure the filter as desired. The mode switch at the top allows the low-pass feedback to be controlled by an external pin (SA/B). Block diagram of one of the filter sections. Adapted from the datasheet. The schematic below is my reverse-engineered schematic of the filter, as implemented on the chip. It closely matches the block diagram, but fills in the details. In the block diagram, the summing circuit (circle) adds one signal and subtracts two signals. This summing circuit is implemented with the three switched capacitors on the left, which act as summing resistors. Note that one switch is grounded during phase 1, while the others are grounded during phase 2; switching the polarity implements addition versus subtraction. The top sum input is either feedback from the low-pass output or ground, selected by an input pin. A CMOS switch is used here, but the switch is static, not clocked, so it doesn't use protection rings and shielding like the other switches. My reverse-engineered schematic of one of the filters. Click this image (or any other) for a larger version. The integrators have switched capacitors on the inputs, acting as resistors. The integration capacitor is either 8 or 16 "squares" of capacitance, selected by a ratio selection pin. This controls the ratio between the clock frequency and the filter frequency, either 50:1 or 100:1.7 Although the integration capacitors are attached to a CMOS switch, the switch is static, so the capacitors act as regular capacitors, not switched capacitors. The op-amps The op-amps are fairly standard CMOS op-amps, built from about 35 transistors. (You might get a lower count if you try counting the transistors below, since some of the blocks are multiple transistors.) The op-amp transistors are much larger than the CMOS switch transistors (very bottom, center). On the die, each op-amp is split into two parts: the differential amplifier on the left and an additional amplification stage on the right. A large capacitor (pinkish) sits between the halves. My first thought was that this was the integration capacitor, but it is just a frequency compensation capacitor, common in many op-amps to stabilize the output. The op-amps also have large transistors next to the output pins; these transistors are functionally part of the op-amps, but located next to the pins to minimize resistance. One of the chip's op-amps. I removed the metal layer to make the transistors visible. One unusual feature of the op-amps is a low-power mode. Pulling a particular IC pin low causes the chip to stop filtering and enter a low-power mode, reducing power consumption by 70%. This is implemented by shutting down the "current mirror" circuits that provide fixed currents to the op-amps and other parts of the chip. The non-overlapping clock generator The MF10 chip is driven by external clock signals, one for each filter, with the frequency of the filter proportional to the clock frequency. The photo of the CMOS switches earlier showed that the clock drives four control lines for the switches. You might think that two control lines would be sufficient: the clock and the inverted clock. The problem is that it is very important to avoid having both switches closed at the same time, even for a moment, as that will short the inputs and corrupt the signals. Instead, the two switches have separate control lines that enforce a small gap between when one switch opens and the other one closes. This is implemented with the circuit below that takes an input clock signal and produces the four outputs that drive the switches. The circuit to generate non-overlapping clock signals. There is a delay between when gate A or B turns on and when the corresponding output changes. The idea behind the circuit is that a phase is blocked from going high until after the other phase goes low, with a pair of inverters providing additional delay. In more detail, suppose the input clock drops from high to low. Gate A will turn off, causing the phase 1 output (ϕ1) to drop after a few gate delays (A delay). Gate B can't turn on until ϕ1 goes low. After additional gate delays, ϕ2 goes high. The behavior is similar when the input clock goes high. Gate B turns off, causing ϕ2 to go low after a delay. This allows gate A to turn on, turning on ϕ1 after more delay. To summarize, after a phase is turned off, there is a delay before the other phase turns on, so the two phases never overlap. The clock-shaping circuitry is implemented with CMOS logic gates. The photo above shows this circuitry under the microscope, with the metal layer removed. The rectangular blocks are doped silicon that forms transistors. The darker regions on the left are NMOS transistors and the lighter regions on the right are PMOS transistors. A CMOS gate consists of NMOS and PMOS transistors working together. The PMOS transistors are larger because PMOS transistors are slightly less efficient than NMOS transistors. The dark circles are contacts between the silicon and the metal layer on top. The copper-colored lines are not metal but a special type of silicon called polysilicon. When a polysilicon line crosses doped silicon, it forms the gate of a transistor. The pinks and greens are due to thin-film interference from a thin layer of oxide that didn't completely dissolve; the silicon is actually gray. The ternary input A weird feature of the chip is the input pin that selects the ratio between the input clock and the filter frequency. In effect, this is a digital input with three values. Tying the pin to the high supply voltage selects a 50:1 ratio. Tying the pin to the midpoint between the supply voltages selects a 100:1 ratio. Pulling the pin to the low supply voltage stops the filter and puts the chip into a low-power mode.8 To handle the three-level input, the input goes through two separate buffers, one that transitions at a lower voltage and one that transitions at a higher voltage. Thus, the two buffers separate the middle signal level. Each buffer consists of a special inverter feeding into a regular inverter. Before explaining the special inverters, I'll review how a regular CMOS inverter works. A CMOS inverter is constructed from a PMOS transistor and an NMOS transistor. When the input is high, the NMOS transistor turns on and pulls the output to ground. When the input is low, the PMOS transistor turns on and pulls the output high. Thus, the input signal is inverted. A CMOS inverter is constructed from a PMOS transistor and an NMOS transistor. In the die photo, you can see the four PMOS transistors (light gray) and four NMOS transistors (darker), forming four inverters. When a polysilicon line (copper-colored) crosses a doped silicon region, it forms the gate of a transistor. For this picture, I dissolved the metal layer in acid so the transistors are visible. The metal layer connected the transistors to complete the wiring of the inverters: it connects the two "out1" contacts to "in2" and connects the two "out2" contacts to the rest of the chip. For the second buffer, "out3" connects to "in4" and so forth. The four inverters that handle the ternary input. I flipped the image to make the orientation better. In this circuit, the length of the transistor gates is varied to make the inverters activate at different voltage levels. Six of the transistor gates are normal (orange arrows); the PMOS gates are wider (in the vertical direction) than the NMOS gates because PMOS transistors are inherently weaker. However, two of the transistor gates are unusually long (horizontal direction, red), making the transistors weak since the current must travel a longer distance. The inverter on the left has a weak PMOS transistor. If the input is high or low, the inverter will operate normally. But if the input is in the middle, both transistors will partially turn on. Since the PMOS transistor is very weak, the NMOS transistor will "win", pulling the output low. Thus, the leftmost inverter treats a medium-level input as a 1, outputting a 0. The third inverter is the opposite; the NMOS transistor has a long, winding gate, so it is weak. In this case, a medium-level input will partially turn on both transistors, but the PMOS transistor will "win", pulling the output high. To summarize, the two inverters have opposite behavior for a middle-level signal, allowing the three input levels to be distinguished. Since the output from a special inverter may be weak, the output goes to a normal inverter to amplify the signal. Conclusions Like most semiconductor companies, Harris has a complicated history. Harris started way back in 1895 as a printing press company. Harris moved into high technology in the 1950s and 1960s, acquiring various radio and electronics companies. In particular, Harris entered the IC business in 1967, when it acquired Radiation, Inc., renaming it Harris Semiconductor a few years later. (We've encountered some Radiation modules in Apollo systems, but I haven't written about them yet.) Harris got out of the semiconductor business in 1999, spinning off Intersil, which was later acquired by the Japanese semiconductor firm Renesas. In 2019, Harris merged with L3 Technologies to become L3Harris, the eighth-largest defense contractor in the US. As for switched-capacitor filters, they have lost popularity as filtering is now more easily done in the digital domain. Texas Instruments acquired National Semiconductor (and the MF10) in 2011; TI's website shows the MF10 as active but expensive and out of stock, so it's probably no longer being manufactured. State variable filters are still used in the synthesizer world both because of their flexibility and because they provide low-pass, band-pass, and high-pass filters in one unit. For more, follow me on Bluesky (@righto.com), Mastodon (@[email protected]), or RSS. Thanks to CuriousMarc for providing the IC. AI statement: Despite the presence of the em dash, no AI was used in the writing of this article (details). Notes and references Once we found the "HF-10" part number, a search turned up a National Semiconductor databook that confirmed that the Harris HF-10 was a direct replacement for the National Semiconductor MF10. It remains a mystery why the Harris chip is externally labeled "F1-10-5" rather than "HF-10". This format doesn't resemble other Harris part numbers. I would suspect a military part number, but it is completely different from the military formats that I've seen on other chips, such as JM38510 numbers or NSN numbers. ↩ You might wonder why the larger capacitors are formed by connecting eight smaller capacitor squares, rather than making one capacitor that is eight times as big. The reason is to get better matching between the two capacitor sizes. A capacitor that is eight times as large won't have exactly eight times the capacitance due to factors such as the behavior of the electric field around the edge of the capacitor, inaccuracies that may make the capacitor slightly larger or smaller than desired, or etching variability around the edges. By building larger capacitors out of identical smaller capacitors, the values can match very well, up to ±0.01% according to The Art of Analog Layout. (With laser trimming, matching of ±0.001% is possible, but that is much more accuracy than the MF10 required.) ↩ Most chips from this era have a single layer of polysilicon, so I was surprised to find two layers in this chip. I've seen two layers of polysilicon before, in the MK4116 DRAM chip and AMD's LANCE Ethernet chip. In both cases, the second layer of polysilicon was used for storage devices. ↩ A standard op-amp integrator is an inverting integrator, and the output is negative. However, the MF10 uses the four-switch switched capacitor that inverts the input voltage. The two negatives cancel out, so the MF-10's integrator is a non-inverting integrator. See Introducing the MF10: A Versatile Monolithic Active Filter Building Block for details. ↩ To remove the metal layer, I used Whink rust stain remover (1.5-3.5% HF) to remove the oxide layer and hydrochloric acid to dissolve the metal. I applied Whink for 20 minutes and HCl for 16 minutes in total. I alternated each chemical for about 3 minutes each, applying a few drops at a time. I examined the die under the microscope after each application to gauge the progress. I stopped at this point since the metal was removed and the underlying transistors were visible. Moreover, the silicon became differentially stained, with NMOS transistors significantly darker than PMOS transistors. Some more Whink would probably improve the appearance of the die, but the risk is that the polysilicon might get removed, which would be bad for reverse engineering. In other words, I'd rather stop too early than destroy the features that I want to see. ↩ For reference, the full block diagram of the chip is below, from the datasheet. Block diagram of the MF10 from the Texas Instruments datasheet. ↩ The filter frequency of the MF10 can be set to either the clock frequency divided by 50 or divided by 100. You might wonder where these ratios come from, since the capacitors on the chip are in 8:1 or 16:1 ratios, not 50:1 or 100:1. The formula for a switched-capacitor integrator is that the filter frequency is the clock frequency divided by 2π times the capacitor ratio. (This can be derived from the op-amp integrator formula and the equivalent resistance of a switched capacitor.) It turns out 2π×8 is 50.27 and 2π×16 is 100.5, providing the 50 and 100 values. Note that these values aren't exactly 50 and 100; they are off by 0.5%. Curiously, the datasheet specifies that the typical frequency error is ±0.2%, significantly smaller. I suspect that the explanation is that the capacitor ratio is not precisely 16:1, due to stray capacitance in the wiring and other factors, and the designers ensured that these factors tweaked the ratio in the desired direction. ↩ I suspect that the ternary input pin was used because the chip didn't have enough physical pins for all the functions they wanted. Note that the two filters are entirely independent, even with separate clocks, except for the 50/100 ratio control and the A/B mode control. I'm sure that these two functions would have independent control pins if the chip had pins available. They could have used a standard 24-pin package for the chip rather than the somewhat unusual 20-pin package, but maybe they had a motivation for avoiding a much larger 24-pin package. ↩
There was a time I'd look at a board like the Radxa Dragon Q8B (at left, above) and be like, "there's no way I'd spend $209 on an SBC with 8 gigs of RAM". But we're in 2026, and seeing the 8 gig Raspberry Pi 5 going for almost the same amount, I figured I'd give it a shot. On paper, the Q8B beats the Pi 5 in pretty much every way. A lot of that is thanks to this Snapdragon 8cx Gen 3 chip, which is the same chip I tested on Microsoft's Windows Dev Kit 2023.
The Sting belongs in the pantheon of films I'm deeply embarrassed to have not watched earlier. Not just because it's a great film — and it is — but because it is so incredibly my shit that I feel retroactively spurned for not having watched it sooner.
If everything worked as well as the product called Evapo-Rust, the world would be a much better place. That’s just one of the many lessons learned during my recent — successful! — project to transform my old, nonfunctioning gasoline-powered generator into something much better.