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Microcode in Intel's 8087 floating-point chip: the scale instruction In the 1970s, floating-point arithmetic was a mess. Computer manufacturers had a dozen incompatible...
2 weeks ago
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Microcode in Intel's 8087 floating-point chip: the scale instruction

from Ken Shirriff's blog [alt+shift+b] in technology

2 weeks ago
In the 1970s, floating-point arithmetic was a mess. Computer manufacturers had a dozen incompatible arithmetic standards. Moreover, floating-point systems were designed around hardware simplicity rather than mathematical rigor, leading to problems with numerical stability. This...
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Cores in space: The core memory module from a 1980 Spacelab computer Spacelab was a reusable laboratory that could be carried in the Space Shuttle's cargo bay, providing...
30th Aug 2026
1

Cores in space: The core memory module from a 1980 Spacelab computer

from Ken Shirriff's blog [alt+shift+b] in technology

30th Aug 2026
Spacelab was a reusable laboratory that could be carried in the Space Shuttle's cargo bay, providing lab space for astronauts and experiments.1 Because Spacelab was a European project, it used a French-built minicomputer, the Mitra 125 MS,2 rather than the Shuttle's main...
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Energizing a vacuum-tube flip-flop module from a 1948 IBM system In 1948, IBM introduced the 604 Electronic Calculating Punch. This machine was a programmable...
31st Jul 2026
1

Energizing a vacuum-tube flip-flop module from a 1948 IBM system

from Ken Shirriff's blog [alt+shift+b] in technology

31st Jul 2026
In 1948, IBM introduced the 604 Electronic Calculating Punch. This machine was a programmable calculator, about the size of a double refrigerator. It was not quite a computer, but was programmed by plugging wires into a plugboard. This machine read numbers from a punch card,...
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Powering up a module from the IBM 604: an electronic calculator from 1948 1948 was an interesting time for computing. For decades, businesses had used punch card equipment...
7th Jun 2026
1

Powering up a module from the IBM 604: an electronic calculator from 1948

from Ken Shirriff's blog [alt+shift+b] in technology

7th Jun 2026
1948 was an interesting time for computing. For decades, businesses had used punch card equipment that added and sorted electromechanically. Now these electromechanical relays and counting wheels were being used to build room-filling general-purpose computers such as Harvard Mark...
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Reverse engineering circuitry in a Spacelab computer from 1980 Spacelab was a reusable laboratory that could be carried in the cargo bay of the Space Shuttle,...
23rd May 2026
1

Reverse engineering circuitry in a Spacelab computer from 1980

from Ken Shirriff's blog [alt+shift+b] in technology

23rd May 2026
Spacelab was a reusable laboratory that could be carried in the cargo bay of the Space Shuttle, providing lab space for astronauts and experiments. Spacelab was controlled by a French-built minicomputer, called the Mitra 125 MS. Unlike modern computers, this computer didn't...
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The electromechanical angle computer inside the B-52 bomber's star tracker Before GPS, how did aircraft navigate? One important technique was celestial navigation: navigating...
18th Apr 2026
1

The electromechanical angle computer inside the B-52 bomber's star tracker

from Ken Shirriff's blog [alt+shift+b] in technology

18th Apr 2026
Before GPS, how did aircraft navigate? One important technique was celestial navigation: navigating from the positions of the stars, planets, or the sun. While celestial navigation is accurate, cannot be jammed, and doesn't require any broadcast infrastructure, it is a difficult...
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The rise and fall of IBM's 4 Pi aerospace computers: an illustrated history The morning of April 12, 1981, 20 years to the day after Yuri Gagarin became the first person in...
29th Mar 2026
1

The rise and fall of IBM's 4 Pi aerospace computers: an illustrated history

from Ken Shirriff's blog [alt+shift+b] in technology

29th Mar 2026
The morning of April 12, 1981, 20 years to the day after Yuri Gagarin became the first person in space, the Space Shuttle thundered into the Florida sky. Commander Young and Pilot Crippen were at the controls as the Shuttle ascended on its first flight. But the launch, like much...
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Instruction decoding in the Intel 8087 floating-point chip pre {border:none;} In the 1980s, if you wanted your IBM PC to run faster, you could buy the Intel...
14th Feb 2026
1

Instruction decoding in the Intel 8087 floating-point chip

from Ken Shirriff's blog [alt+shift+b] in technology

14th Feb 2026
pre {border:none;} In the 1980s, if you wanted your IBM PC to run faster, you could buy the Intel 8087 floating-point coprocessor chip. With this chip, CAD software, spreadsheets, flight simulators, and other programs were much speedier. The 8087 chip could add, subtract,...
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Notes on the Intel 8086 processor's arithmetic-logic unit In 1978, Intel introduced the 8086 processor, a revolutionary chip that led to the modern x86...
23rd Jan 2026
1

Notes on the Intel 8086 processor's arithmetic-logic unit

from Ken Shirriff's blog [alt+shift+b] in technology

23rd Jan 2026
In 1978, Intel introduced the 8086 processor, a revolutionary chip that led to the modern x86 architecture. Unlike modern 64-bit processors, however, the 8086 is a 16-bit chip. Its arithmetic/logic unit (ALU) operates on 16-bit values, performing arithmetic operations such as...
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The stack circuitry of the Intel 8087 floating point chip, reverse-engineered Early microprocessors were very slow when operating with floating-point numbers. But in 1980, Intel...
9th Dec 2025
1

The stack circuitry of the Intel 8087 floating point chip, reverse-engineered

from Ken Shirriff's blog [alt+shift+b] in technology

9th Dec 2025
Early microprocessors were very slow when operating with floating-point numbers. But in 1980, Intel introduced the 8087 floating-point coprocessor, performing floating-point operations up to 100 times faster. This was a huge benefit for IBM PC applications such as AutoCAD,...
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