Posts
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
@dnaunton The SR-71 used a different system, the NAS-14V2 astroinertial navigation system. Nortronics built the SR-71 system and Kollsman built the B-52 system. The B-52 system is said to have also been used in the Hound Dog cruise missile. A very detailed document on the SR-71 star tracker is here: https://audiopub.co.kr/wp-content/uploads/2021/10/NAS-14V2-ANS-System.pdf
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
@vk2bea They say that the accuracy was within 0.1 degree.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
@numodular Although this unit looks like a gyroscope, it is not at all a gyroscope. There is nothing spinning.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
For more on the electromechanical Angle Computer, see my article: https://www.righto.com/2026/04/B-52-star-tracker-angle-computer.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
This close-up of the Angle Computer shows the complexity of the gears inside. The thicker brass-colored cylinders are differential gears that add two signals using rotations.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
The back of the Angle Computer has devices called synchros that read out the star's position relative to the aircraft. At the bottom, motors drive the mechanism.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
Inside the Angle Computer, a star pointer corresponds to the position of the star on the celestial sphere. Gears move the pointer to match the star's coordinates (called the declination and Local Hour Angle).
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
The "Astro Tracker" was the heart of the celestial navigation system. The 4-inch clear bubble stuck out from the top of the aircraft to view the stars. Inside, a telescope and photomultiplier tube tracked a star, steered by motors and prisms.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
2d ago
In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
@urwumpe Fair enough :-)
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
I forgot to explain the 4 Pi name. IBM's System/360 mainframes got their name because they supported a full 360º circle of applications, from business to scientific. The 4 Pi aerospace computers, however, were designed for the 3-D world, a "sphere" of applications. While a circle has 360º, a sphere has 4π steradians of solid angle.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
There were many more models of System/4 Pi computers, including refrigerator-sized computers used on submarines; see my article for details: https://www.righto.com/2026/03/ibm-4-pi-computer-history.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
In 1991, the Space Shuttle upgraded its computer to the AP-101S, replacing two 60-pound boxes with one box. Since there were five computers on the Shuttle, this change freed up 300 pounds for additional cargo. The CPU was implemented in three boards full of chips, one below. These boards were much larger than the earlier 4 Pi boards.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
The Space Shuttle used a more advanced System/4 Pi computer called the AP-101B. A separate computer, the I/O Processor, provided 24 data buses to all parts of the Shuttle. These boxes still used individual TTL chips and magnetic core memory.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
IBM's 4 Pi computers were built from simple TTL integrated circuits and used magnetic core memory for storage. "Flat-pack" integrated circuits on multi-layer circuit boards provided dense logic. The board below was round to fit inside a tactical missile, but most of the computers used standardized rectangular boards called "pages".
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 29, 2026
In 1967, IBM introduced the System/4 Pi line of aerospace computers, packing mainframe performance into a compact box. 4 Pi computers powered everything from military aircraft to the Space Shuttle to sonar systems on submarines. Thread...
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
@raymaccarthy The 8087 doesn't help with 16-bit integer math.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
@Sonic2k Early calculator chips are pretty weird. They operate in decimal and are serial, so they operate on one bit at a time with a one-bit ALU. So all the data is constantly in motion.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
Instruction decoding in the 8087 has many more complications: hardcoded instructions handled by the "Bus Interface Unit", instructions that load a constant from the constant ROM, and handling the instruction queue. For more details, see my latest blog post:
https://www.righto.com/2026/02/8087-instruction-decoding.html
https://www.righto.com/2026/02/8087-instruction-decoding.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
The microcode inside the 8087 chip uses conditional jumps for many purposes. Some conditions examine the instruction, so the microcode can act differently for different instructions. Here's the PLA that stores target addresses for microcode jumps. Target 0 is special: it does a three-way branch depending if the instruction is multiplication, division, or addition/subtraction.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
Like many processors, the 8087 uses a "Programmable Logic Array" (PLA) to decode the bit patterns in instructions. A PLA consists of grids of transistors, with some of the transistors missing. The pattern of transistors controls the PLA's function. The grid is a dense and flexible way of implementing this logic.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 14, 2026
In 1980, Intel released the 8087 floating-point chip, making math much faster. I'm reverse-engineering this chip, 46 years later. Most of its instructions are implemented in microcode, but some are implemented in hardware. Let's look at the circuitry that decodes instructions and decides what to do...
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 04, 2026
For details on the Algorithms of Love event tonight, see the Computer History Museum page. It also has a link to watch the event live on YouTube.
https://computerhistory.org/events/algorithms-of-love/
https://computerhistory.org/events/algorithms-of-love/
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Feb 04, 2026
Back at the keypunch, I typed the text "ALGORITHMS OF LOVE" on one card. I could then use the punch to duplicate this text onto my stack of 100 heart cards. It duplicates about 10 characters per second, so much faster than typing, but still a bit tedious. The final result was the card with printed text at the left and the heart (without text) at the right.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Dec 30, 2025
If you're interested in obscure details of the microcode in the Intel 8087 floating-point chip, I have a new blog post...
https://www.righto.com/2025/12/8087-microcode-conditions.html
https://www.righto.com/2025/12/8087-microcode-conditions.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 03, 2025
@murtaugh @futurebird Yikes!
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 03, 2025
@azonenberg From the application note, I think the main issue is if the VCO locks onto a sideband, then you get distorted audio. It's better to replace this with white noise so the user knows that the tuning is off.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
@StumpyTheMutt That must have been frustrating! I read that this chip was very sensitive to the board layout so something subtle might have thrown it off.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
Credits: Thanks to IEEE for providing the die photo.
Wristwatch photo from a Philips article: https://www.cool386.com/tda7000/technical_review.pdf
Lots more information on the TDA7000 chip here: https://www.cool386.com/tda7000/tda7000.html
Application note with details here: https://www.tel.uva.es/personales/tri/radio_TDA7000.pdf
Wristwatch photo from a Philips article: https://www.cool386.com/tda7000/technical_review.pdf
Lots more information on the TDA7000 chip here: https://www.cool386.com/tda7000/tda7000.html
Application note with details here: https://www.tel.uva.es/personales/tri/radio_TDA7000.pdf
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
The chip uses these components to turn an FM radio signal into audio by combining an oscillator, mixers, filters, amplifiers, and other circuits. If you want to know more about this FM radio chip, I go into great detail in my blog post: https://www.righto.com/2025/08/reverse-engineering-analog-TDA7000.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
The most unusual components in the chip are the "varicap diodes", which help adjust the radio's frequency. These special diodes act as capacitors with a value that can be controlled by changing the voltage.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
Another important part of the chip is the resistors, which impede the flow of electricity. They are typically long and zig-zagging. The ends of the resistors are connected to the metal wiring. The arrows indicate the holes in the insulating oxide layer where these contacts take place.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
Transistors are the main components of the chip, amplifying signals and performing other functions. Modern chips use CMOS transistors, but this chip uses NPN and PNP transistors. These diagrams show how the transistors look on the die, along with cross sections showing the silicon layers.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
This close-up of the die shows how the metal wiring (white lines) connects the underlying silicon structures (gray and green). Unlike modern chips, this chip only has one layer of metal, so the wiring needs to twist and turn when other wires get in the way.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
Here's a die photo of the FM radio chip, the TDA7000. You can see the greenish silicon, with white metal wiring on top. The 18 white squares around the edges are the bond pads that connect the die to the chip's pins, with gold wires attached. I've labeled the main functional blocks of the chip. 2/N
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Aug 02, 2025
In 1983, Philips produced the first FM radio receiver on a chip, leading to products such as the FM radio wristwatch. Let's look at the tiny silicon die inside this chip and see how it works. 1/N
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
@cameron_talley The keyset encoding is essentially binary.
https://oldbytes.space/@kenshirriff/114212671748858127
https://oldbytes.space/@kenshirriff/114212671748858127
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
@teajaygrey It's a complex situation. It doesn't help that according to the patent, Engelbart invented the mouse.
https://patents.google.com/patent/US3541541A
https://patents.google.com/patent/US3541541A
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
@bitsavers @simonzerafa Al, we are grateful to you for the Alto boards that you supplied to us. Not to mention your work with bitsavers, which has been crucial to many of our projects.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Thanks to Christina Engelbart for loaning me the keyset.
Credits: images of the demo are from the recorded demo: https://www.youtube.com/watch?v=UhpTiWyVa6k
SDS 940 diagram from http://www.bitsavers.org/pdf/sds/9xx/940/980126A_940_TheoryOfOperation_Mar67.pdf
Credits: images of the demo are from the recorded demo: https://www.youtube.com/watch?v=UhpTiWyVa6k
SDS 940 diagram from http://www.bitsavers.org/pdf/sds/9xx/940/980126A_940_TheoryOfOperation_Mar67.pdf
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
For more on Engelbart, the Mother of All Demos, and my keyset interface, see my blog post:
https://www.righto.com/2025/03/mother-of-all-demos-usb-keyset-interface.html
https://www.righto.com/2025/03/mother-of-all-demos-usb-keyset-interface.html
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Engelbart's software ran on a large Scientific Data Systems (SDS) 940 computer. Microwave links and modems connected the computer to the demo, 30 miles away.
To get into computing, Xerox later bought SDS, spending $8 billion (current dollars) on a disastrous acquisition.
To get into computing, Xerox later bought SDS, spending $8 billion (current dollars) on a disastrous acquisition.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
This reference card explains what keyset presses and mouse buttons generate each character. Memorize this chart and then you too can use the keyset. A much steeper learning curve than the mouse.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Here's the vintage keyset with my USB interface. I used an Arduino-like microcontroller (the Teensy) to make the keyset act like a standard USB keyboard. To get upper case and special characters, you click mouse buttons at the same time. Too much coordination for me!
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Engelbart's daughter, Christina Engelbart, loaned me a keyset, so I built a USB interface for it and plugged it into my laptop. I had a hard time using the keyset and I'm not surprised it didn't catch on. Supposedly it takes "only" a week to learn, too long for me.
https://www.youtube.com/watch?v=DpshKBKt_os
https://www.youtube.com/watch?v=DpshKBKt_os
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
In 1994, Wired writer Steven Levy wrote a book "Insanely Great: The Life and Times of Macintosh, the Computer that Changed Everything". He discussed how Engelbart influenced the Mac, calling the 1968 demo "the mother of all demos". The name stuck, ensuring the fame of Engelbart's demo.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Engelbart's demo was later called "The Mother of All Demos". But first, an Intel demo at Comdex got that name. In 1990, Iraq invaded Kuwait and Saddam Hussein promised "The Mother of All Battles" in the Gulf War. "The mother of all..." became a meme, applied to many things including Intel's demo.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
In the 1970s, some members of Engelbart's team moved to Xerox PARC. They put his concepts into the Xerox Alto, giving it a keyset, mouse, and graphical user interface. Steve Jobs toured PARC, taking the mouse and GUI ideas for the Apple Lisa and the Macintosh. But he left the keyset behind.
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
Engelbart's demo was like a PowerPoint presentation over Zoom, projected onto a large screen. He collaborated with co-workers 30 miles away, talking with them, editing shared files, browsing the code online, and clicking links with the mouse (which he invented). Impressive for 1968!
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Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
Ken Shirriff
@kenshirriff@oldbytes.space
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Xerox Alto. Ex-Google, Sun, Msft. So-called boffin.
oldbytes.space
@kenshirriff@oldbytes.space
·
Mar 23, 2025
In 1968, Douglas Engelbart revolutionized computing by showing the mouse, hypertext, and collaborative computing in "The Mother of All Demos". Most of his ideas are now part of everyday computing, but one device—the keyset—failed to catch on. Let's look at Engelbart's demo and the keyset. 1/N
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