iiinova — where your digital self keeps evolving

Ken Shirriff @righto.com · 26/09/2026

How do computers calculate complicated trig functions such as tangent? I took a look at Intel's 8087 floating-point chip under the microscope to find out. The chip combines two techniques to evaluate the tan function quickly and accurately: polynomials and an algorithm called CORDIC...

A die photo of the 8087 chip under a microscope shows complex patterns from its transistors and wiring. The middle of the chip holds the microcode ROM, while the bottom half of the chip is the datapath that performs calculations. Zooming in on the datapath shows various functional blocks, which appear as rectangles with different textures. Important functional blocks are labeled: exponent ROM, constant ROM, shifter, adder, registers, and so forth.

216036

Ken Shirriff @righto.com · 12/09/2026

In 1980, Intel introduced the 8087 floating-point coprocessor chip. Plugging this chip into your IBM PC made math 100 times faster, good for CAD and spreadsheets. I opened up the chip to reverse-engineer exactly how it does complicated calculations. Let's take a look inside...

The integrated circuit is a black ceramic rectangle with 40 metal pins sticking out, in two rows. (This is known as a DIP, a Dual Inline Package.) It has three rows of text: "D8087-1", a cryptic version label, and then the copyright line with a big lower-case I, INTEL m c 1980 1984. The m and c are in circles for the mask-work symbol and the copyright symbol. The chip has a small semicircular notch on the left side, indicating its orientation. The package consists of two thin ceramic layers, bonded together with a gray substance; the metal pins stick out from this gray substance. The ceramic package is important to me because tapping the gray layer with a chisel will cause the two layers to separate, revealing the silicon die inside. In contrast, most chips are in epoxy packages, which are very difficult to open, usually requiring strong acids.

722349

Ken Shirriff @righto.com · 30/08/2026

Before semiconductor RAM, most computers used magnetic core memory. This is the 32 KB core stack from the computer on Spacelab, the Space Shuttle's experimental laboratory. Let's take a closer look...

The core stack from the Spacelab computer. This is a stack of six rectangular circuit boards, joined by blue connectors on each end. The cores are visible on the top board. The 294,912 cores are way too small to see; there are eight large reddish-brown squares, each holding a region of cores. 18 reddish and greenish stripes are slightly visible, showing regions for the 18 bits of storage.

218345

Ken Shirriff @righto.com · 31/07/2026

This vacuum tube module was used in an IBM programmable calculator from 1948. This module, called a "trigger", stored one bit of information. Let's take a closer look and see the module operate.

A cylindrical tube module. It consists of a U-shaped metal frame forming a handle, with a vacuum tube and some electronic components (resistors and capacitors) mounted on insulating disks. At the bottom of the module, nine metal pins allow the module to be plugged into a socket.

111021

Ken Shirriff @righto.com · 28/06/2026

The Space Shuttle had five general-purpose computers that controlled, monitored, and navigated the Shuttle. Each computer consisted of two boxes: the CPU (right) and the I/O Processor (IOP, left). The IOP connected the computer to 24 high-speed networks. Let's look at two boards from the IOP... 1/N

Two rectangular aluminum-alloy boxes, each about 10″ × 7.5″ × 22.5″. Each box has two rectangular handles on the front, as well as multiple round military-style connectors. Each box is marked "Caution: weight over 45 pounds."

Two circuit boards, crammed with chips. Each board is 9"×3.5" with a metal frame and thumbscrews on either side. Each board has a green 120-pin connector at the bottom; the connector on the top board is broken.

The top board is a network interface board. It is dominated by four large golden integrated circuits as well a large golden hybrid module. The rest of the board has five rows of tiny black flat-pack integrated circuits, each smaller than a fingernail. There are a few discrete components: resistors, capacitors, inductors, transformers.

The second board has standard DIP (dual-inline package) integrated circuits. Most of them are white ceramic with gold lids, interspersed with regular black integrated circuits. The chips are mostly arranged in three rows, but three integrated circuits are arranged horizontally.

413427

Ken Shirriff @righto.com · 13/06/2026

Intel introduced the 8087 floating-point chip in 1980 to make math faster. The chip does tangents, square roots, and so forth, but fundamentally everything is computed through additions and subtractions, performed by an adder at the heart of the chip. Let's look at the adder's circuitry... 1/N

$A die photo of the 8087 chip, with functional blocks labeled. The die has complex patterns with roughly rectangular shapes. Around the edges, thin bond wires connect the die to the chip's 40 external pins. In the bottom center, the adder is highlighted. It is a tall, thin rectangle in the middle of the "fraction datapath". Above it is the exponent datapath.$

312733

Ken Shirriff @righto.com · 07/06/2026

The IBM 604 Electronic Calculating Punch was introduced in 1948. Not quite a computer, it was a programmable calculator that became very popular due to its low price of $550/month, and over 5600 were produced. I have a vacuum tube module from this system, so I powered it up... 1/N

Black and white photo of the IBM 604 Electronic Calculating Punch behind a Type 521 Card Reader/Punch. The IBM 604 is about the size of two refrigerators. It's a dark gray box with art deco-ish chrome trim. The Card Reader/Punch is slightly smaller but the same style. It has a hopper on top for inserting a stack of punch cards.

A thyratron tube module from the IBM 604 Electronic Calculating Punch.
The module consists of a vacuum tube in a U-shaped metal frame with pins at the bottom. The vacuum tube is a glass cylinder with a peak at the top and some metal inside. Some resistors and capacitors are mounted between the tube and the pins. The U-shaped frame functions as a handle so the module can be pulled out and replaced.

45610

Ken Shirriff @righto.com · 30/05/2026

In the 1980s, if you wanted your IBM PC to be faster for spreadsheets or CAD, you could buy the Intel 8087 floating-point chip. Internally, the chip runs special code called microcode. We opened the chip, extracted the microcode, and are figuring out how it works. 1/n

The 8087 chip is a black rectangle with 40 metal pins along its long sides. This package is known as a DIP (dual inline package). Unlike modern chips, this chip is a ceramic package. Text on the chip includes "D8087-1" "Intel copyright 1980 1984"/

1029464

Ken Shirriff @righto.com · 23/05/2026

The Space Shuttle could hold a flying laboratory called Spacelab in its cargo bay. Three French-made computers ran Spacelab. I opened up a Spacelab computer and found that instead of a microprocessor, it is built from a multitude of simple chips. Let's take a closer look at the computer...

The computer is a shiny metal box, roughly the size of a toaster oven. It has two handles on the front, as well as six round military-style connectors. The computer is labeled "cimsa", the manufacturer. I took the top of the computer, so you can see the 36 circuit boards inside. The photo shows a close-up of one of the circuit boards. The board contains 28 rectangular integrated circuits. Three of the integrated circuits are much larger than the others.

2753584

Ken Shirriff @righto.com · 18/04/2026

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...

The Angle Computer is a complicated electromechanical system with gears, motors, and bundles of wires. It has a grey metal shell that includes a half sphere. Inside this sphere, arms move a star pointer to indicate the position of a star. Other gears and mechanisms read out the position.

413827

Ken Shirriff @righto.com · 29/03/2026

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...

The TC-2 computer was used on the A-7 Corsair II aircraft. The computer is a gray box, a bit under a cubic foot. It has round military-style connectors on the front, as well as a black fan. It has stencilled text: "Caution: Weight over 60 pounds", "Grip Area Underneath". The fan has a red warning label: "No step. No lift. High temperature." Photo courtesy of Alex1970-14.

The AP-101S is the upgraded Space Shuttle computer. It is a rectangular metal box with U-shaped metal handles on the front, as well as round military-style connectors. The cover is removed, revealing about a dozen large circuit boards inside, as well as a large bundle of yellow and black wires.

112137

Ken Shirriff @righto.com · 14/02/2026

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.

A die photo of the 8087 chip, with the main functional blocks labeled. The chip is a tan rectangle with complex patterns in dark brown. Many of the patterned regions are textured rectangles. One of the largest rectangles is the microcode ROM in the middle. The bottom half of the chip is the datapath, performing operations on floating-point numbers. The instruction decoding happens in the upper left. Around the edges of the chip, bond wires connect the chip to the 40 external pins, but the pins are not visible, just short segments of the bond wires.

213829

Ken Shirriff @righto.com · 23/01/2026

The arithmetic/logic unit (ALU) in the Intel 8086 processor (1978) is more complicated than you might expect, performing 28 different operations from addition and logical AND to shifts and BCD adjustment. A special control circuit reconfigures the ALU for each operation. Let's look closer...

A die photo of the 8086 microprocessor. The image shows a tan square with complex patterns of beige and dark lines showing the circuitry. Thicker light lines distribute power across the chip while black bond wires are attached around the edges. Various regions with different patterns are labeled with their function including a large rectangular region in the lower right that holds the microcode and the 16-bit ALU in the lower left. The ALU Control circuit at the bottom is highlighted.

27614

Ken Shirriff @righto.com · 09/12/2025

In 1980, Intel announced the 8087 Math Coprocessor, a chip that made floating-point 100 times faster. I opened up the chip, took photos of the silicon structures, and analyzed its circuitry. It's a very complex chip for its time. Let's take a look inside...

A photo of the 8087 die under a microscope. The die is rectangular, with complex patterns in purplish-brown. The patterns consist of rectangular regions, striped regions in the bottom half of the chip, and other more irregular regions.

At the right, two regions are highlighted in red: the registers and the stack control circuitry.

Around the edges of the die, you can see the hair-thin bond wires that connect the chip to its 40 external pins. The complex patterns on the die are formed by its metal wiring, as well as the polysilicon and silicon underneath. The bottom half of the chip is the "datapath", the circuitry that performs calculations on 80-bit floating point values. At the left of the datapath, a constant ROM holds important constants such as π. At the right are the eight registers that form the stack, along with the stack control circuitry. The chip's instructions are defined by the large rectangular microcode ROM in the middle.

412734

Ken Shirriff @righto.com · 22/11/2025

Intel's 386 processor (1985) was critical to the success of Intel. With 285,000 transistors, it was too much for Intel's design process and the schedule started slipping. Intel pivoted to "standard cells", an automated technique for chip layout to get back on track. Let's look closer...

A die photo of the 386 processor. It is a square with complicated patterns on top. Under the microscope, the circuits appear in dark purple. Parts of the chip have been marked with boxes: these are standard cell circuits and have a distinctive striped appearance.

39815

Ken Shirriff @righto.com · 18/10/2025

The New York Times recently introduced daily puzzles called Pips. You place the dominoes on the grid so the numbers satisfy the labels. I solved Pips with cool software called a constraint solver. You give the constraints, e.g. "sum to 8", and it "magically" finds a solution. Let's look closer...

A three-by-three grid of squares with four dominoes below it. Two squares are labeled with "8", indicating that the numbers in that region must sum to eight. Another square is labeled "<5", indicating that the number in that square must be less than 5. The three bottom squares are labeled with an equals sign, indicating that the three numbers must be the same. The upper-right square is missing so there are 8 squares in total, able to hold four dominoes.

4509

Ken Shirriff @righto.com · 02/10/2025

We fixed the vintage IBM printer at the Computer History Museum yesterday. Introduced in 1959, the IBM 1403 line printer provided fast, high-quality output, printing 132 character lines. Unfortunately, one column stopped printing, so we disassembled the printer to fix a bad hammer. Keep reading...

The IBM 1403 line printer is a large unit on a stand, printing on green-bar paper that feeds in at the bottom. The printer is dark gray with a clear plastic cover over the printer and a blue panel at the left with a few control buttons. Behind the printer, three 729 tape drives are visible, each about the size of a refrigerator. The IBM 1401 computer is partially visible at the right, about the size of two refrigerators. It has a control panel with lights, switches, and knobs.

49319

Ken Shirriff @righto.com · 24/09/2025

The iPhone 17 is powered by Apple's A19 SoC (System on a Chip). Chipwise took a die photo of the chip, but it's a bit drab. I spiced it up by applying the over-saturated color gradient that Apple used for die photos of the M1 chip :-) Link to the original die photo: chipwise.tech/our-portfoli...

6735

Ken Shirriff @righto.com · 06/09/2025

Celebrated Navajo (Diné) artist Marilou Schultz recently completed a striking weaving. Although this rug may appear abstract, it is a representation of the wiring inside an integrated circuit. It shows the 555 timer, said at one point to be the world's most popular IC. Let's take a closer look...

A Navajo weaving hanging on a wall. The pattern appears abstract: thick white lines in varying directions on a black background. There are some reddish-orange diamonds near the edges, as well as a few thin outlined rectangles. There are three larger squares with a double-H pattern inside. Overall, the pattern looks a bit like an aerial view of roads in a strange ancient city. Thanks to First American Art Magazine for this photo.

5389118

Ken Shirriff @righto.com · 18/08/2025

The latest issue of @science.org mentions a magnetic compound Cr2Gr2Te6. The element Gr confused me, but it turned out to be a typo for Ge, germanium. Strangely, I found multiple papers with the same typo in the same context, so I wrote a short blog post about it. www.righto.com/2025/08/Cr2G...

Text from the journal Science. I've highlighted the formula Cr2Gr2Te6; the rest of the text is not particularly relevant, discussing thin magnetic materials.

2508

Ken Shirriff @righto.com · 17/08/2025

How did Intel's 386 processor connect to the outside world? Tiny wires connect to the bond pads around the edges. Special input/output circuits—visible in zoomed-in blocks—send and receive signals while protecting the chip from dangers that could destroy it. Let's take a look... 1/N

A die photo of the 386 processor. It is a square with complicated patterns on top. Around the edges, 141 square bond pads have tiny gold wires attached to connect the chip to the outside world. In three places, the image zooms in on the bond pads, showing the circuitry associated with the connections.

212326

Ken Shirriff @righto.com · 09/08/2025

Intel's 386 processor was popular in late 1980s microcomputers. From the outside, the 386 chip is a boring ceramic square. But I obtained a 3-dimensional CT X-ray scan from Lumafield, revealing six layers of complex wiring hidden inside the ceramic package. Let's take a closer look... 1/N

An X-ray scan of the 386 chip. It shows a square with a grid of 132 pins. In the middle is a square, the silicon die. Blue wires connect the pins to the chip. Spikes stick out all around the perimeter of the package.

326265

Ken Shirriff @righto.com · 02/08/2025

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

A photo of a digital watch with a tuning knob on the front and earbud headphones plugged into the side. Next to it is the wristwatch with the back removed, revealing the batteries inside, along with tiny surface-mount components and a small black integrated circuit.

310621

Ken Shirriff @righto.com · 21/07/2025

We obtained a mysterious box of 1960s electronics. I reverse-engineered it, and with much effort, we got it running. It turns out to be a test unit for testing NASA's Up-Data Link, a system from the Apollo moon landing to control the spacecraft from the ground. Let's take a look inside... 1/n

A gray box of electronics. It has thirteen large orange digits displayed at the top, with lights and switches underneath. These have labels such as Message, UDL Compare, AGC Confirm, and Program Start. A paper tape reader sticks out of the front, with a paper tape threaded through it. The unit is rack-mountable with two handles on the front.

14682166

Ken Shirriff @righto.com · 19/07/2025

We're at OpenSauce 2025, showing off Apollo hardware, electromechanical computers, the MOnSter 6502, and other treats. Join me, @tubetime.bsky.social, and Mike at the CuriousMarc booth!

Photo of a booth at OpenSauce. Three tables are covered with vintage electronics of various sorts. Mike is working on the Apollo CDU at the left.

515616

Ken Shirriff @righto.com · 14/07/2025

I'll be at OpenSauce 2025 along with @curiousmarc.bsky.social, @tubetime.bsky.social, and Mike. We plan to show some Apollo hardware, atomic clocks, vintage avionics, and who knows what else, so stop by if you're attending. opensauce.com

opensauce.com

Open Sauce 2025 - Open Sauce

A Celebration Of Makers And Creators. A three-day event in San Francisco Bay Area at San Mateo County Event Center. Attendees will explore...

0398

Ken Shirriff @righto.com · 11/07/2025

The Globus is a navigational instrument that uses a rotating globe to show the position of the Soyuz spacecraft above the Earth. Inside the Globus, a complicated system of gears and motors positions the globe. @jonbruner.bsky.social at Lumafield created a three-dimensional X-ray scan for us. 1/4

26915

Ken Shirriff @righto.com · 25/06/2025

In the 1960s, this absurdly large camera was used to make masks for integrated circuits. The layers of the integrated circuit were drawn at large scale and then optically shrunk to make the glass masks that were used in manufacturing.

Black and white photo of a giant bellows camera about 8 feet tall. A man is standing in front of the lens which is the size of his torso. Caption: "A copy camera of the type useful in making high-precision photographic masks."

48021

Ken Shirriff @righto.com · 20/06/2025

Last week, the vintage IBM 1401 computer at the Computer History Museum started behaving strangely: it wouldn't halt. More specifically, if you had two HALT instructions in a row, it would halt for the first, but when you continued, it crashed mysteriously. Here's how we fixed it.... 1/N

The IBM 1401 is a vintage computer about the size of two refrigerators. It has dark gray panels with blue and chrome trim. In the upper left, a control panel has numerous lights and buttons. The large line printer is visible in the foreground. A tape drive with two reels of tape is in the background.

312520

Ken Shirriff @righto.com · 14/06/2025

When landing on the Moon, the astronauts watched an instrument called the FDAI that showed the spacecraft's orientation. The ball inside the Flight Director/Attitude Indicator rotated in three axes as the Lunar Module rotated. Let's look inside and see how it works. 1/N

The FDAI is an octagonal instrument with a rotating ball in the center. The ball is half black and half white, with numbers and lines on it to indicate angles. Three yellow needles direct the astronauts with the desired motion. Three arrow scales on the sides show the spacecraft's roll rate in the three axes. An orange flag labeled "OFF" is visible.
The cover has been removed from the FDAI so some of the internal components are visible.

213038

Ken Shirriff @righto.com · 30/05/2025

This photo of magnetic core memory popped up, taken by Ansel Adams. I investigated a bit: this memory holds 4000 bits, each stored in a tiny magnetized ferrite ring. It may be from an IBM 705 vacuum-tube business computer. 1/N

A photo with the caption "'Hands weaving magnetic-core memory, IBM, Poughkeepsie, New York', 1956. Photograph by Ansel Adams. This photograph was made on a commercial assignment for IBM."

This black-and-white photo shows a core memory plane being assembled. It consists of an 80 by 50 grid of wires in a frame with tiny toroids on the wire intersections. Each wire is attached to metal terminals on the frame. Someone is using tweezers to thread the tiny cores onto the wires. The plane is about 4/5 completed. One hand is below the plane, palm-up, visible through the wires. The other hand (with nail polish) is above the plane, holding tweezers.

1127681

Ken Shirriff @righto.com · 21/05/2025

In the Apollo space program, the FDAI (Flight Director Attitude Indicator) showed the orientation of the spacecraft through a ball that rotates on three axes. The yellow needles and black pointers show error and movement rate. This FDAI was later modified for use in a Space Shuttle simulator.

An indicator with a rotating ball in the middle. The top half of the ball is black and the bottom is white. The ball has various lines and angle markings on it. Three yellow needles project across the ball to indicate the error in each axis. Three scales with needle pointers show the rotation rate in the three axes. The scales are illuminated. Two power wires run to clips attached to the interior of the FDAI, which has its cover removed.

1430

Ken Shirriff @righto.com · 17/05/2025

How thin is spider silk compared to the wiring on a chip? Here's a close-up of a spiderweb strand diagonally across an Intel 386 processor. The spiderweb is 4 µm thick, just a bit thinner than this 1985 chip's 5 µm metal wiring. Wiring in modern chips is 100 times thinner.

A close-up of the die of the Intel 386 processor showing the metal layers. A strand of a spider web runs diagonally across the image. The processor image consists of yellowish metal wiring running horizontally and vertically, with more complex patterns underneath. Black circles indicate connections between the two metal layers. The spider web is about the same thickness as the metal wiring. The silicon circuitry underneath is not visible, but its feature size is 1.5 µm, considerably thinner than the spider web.

27615

Ken Shirriff @righto.com · 16/05/2025

Tape drive repair at @computerhistory.bsky.social. I helped @tubetime.bsky.social figure out why the tape drives wouldn't backspace. The problem turned out to be a bad germanium transistor on an inverter card. 1/5

314821

Ken Shirriff @righto.com · 10/05/2025

Anyone use Intel's 386 processor from 1985, the first 32-bit x86? To improve performance, it preloaded instructions into a 16-byte prefetch queue (highlighted in red). Why does such a small queue take up so much of the chip? Let's look under the microscope at its complicated circuitry... 1/N

A die photo of the Intel 386 processor. It looks a bit like an aerial photo of a weirdly-zoned city, with rectangular blocks of various textures in a complicated arrangement. The functional units of the chip are labeled. In particular, the Prefetch Unit is near the upper left corner. A large red rectangle is labeled Prefetch Queue.

211121

Ken Shirriff @righto.com · 01/05/2025

Intel's 386 processor (1985) moved the x86 architecture to 32 bits, but it needed to be backward compatible with earlier 16 and 8-bit processors. As a result, it needed complicated circuitry for its internal registers: six different circuits for 30 registers. Let's look at the silicon circuits. 1/N

A die photo of the Intel 386 processor under the microscope. The die has complex patterns that make up the different parts of the chip. The various blocks are roughly rectangular with different textures.
The main functional blocks are labeled, including the paging unit, bus interface unit, prefetch unit, segment unit, instruction decode unit, protection test unit, data unit, and control unit. The register file, the subject of this thread, is in the lower left corner, highlighted by a red rectangle. This die photo image has a purple tint.

38710

Ken Shirriff @righto.com · 24/04/2025

If you were following my recent repair of a vintage Commodore PET home computer, you may enjoy this video from @curiousmarc.bsky.social:

youtu.be

Hard to repair Commodore PET

YouTube video by CuriousMarc

1474

Ken Shirriff @righto.com · 13/04/2025

The Commodore PET, along with the Apple II and the Radio Shack TRS-80, formed the "1977 Trinity" that made home computers popular. The PET was very quirky, combining a tiny keyboard, a cassette drive for storage, and a monitor in a trapezoidal case. I got one, but it didn't work. Let's fix it... 1/N

1020134

Ken Shirriff @righto.com · 31/03/2025

The Pentium processor, like many others, implements its instructions in microcode. Each step of an instruction is described by a micro-instruction, stored in the chip in the microcode ROM. This die photo shows the parts of the Pentium. Let's take a quick look at the microcode ROM...1/N

The Pentium chip under a microscope. It is a complex pattern of tan and brown regions, mostly rectangular. I've labeled the main functional blocks, such as the caches, the integer execution unit, the floating point unit, and the microcode ROM.

27416

Ken Shirriff @righto.com · 25/03/2025

Just discovered that Jonah Goldberg, journalist and magazine editor, is a different person from Jeffrey Goldberg, journalist and magazine editor. Things make much more sense now!

0270

Ken Shirriff @righto.com · 25/03/2025

I read an interesting paper on the history of the QWERTY keyboard. The keyboard evolved from an 1859 keyboard with half the alphabet in order and the second half backward. You can still see this ordering on the bottom rows of the modern keyboard, although many keys have moved over the years.

Line drawing of a keyboard for a printing telegraph. Letters A-M are on the top row and letters O-Z are on the bottom row backward. The keyboard is similar to a piano keyboard if black keys were in all the positions.

A Macbook keyboard, showing the letters that are in alphabetical order in the second row and in reverse alphabetical order in the third row. Specifically, the letters are A, D, F, G, H, J, K, L in the second row and M, N, V, X, Z in the third row. Thus, 13 out of 26 letters have the alphabetical pattern.

28212

Reposted by Ken Shirriff

Tube🍂Time @tubetime.bsky.social · 24/03/2025

i've built a reproduction chord keyboard (keyset)! this device was invented along with the computer mouse by Douglas Engelbart's team at SRI back in the 1960s. unlike the mouse, it never took off. files are here: github.com/schlae/engel...

something that looks like a small white piano keyboard with only 5 keys (and no black keys). there's a grey cable coming out of the back.

48010

Ken Shirriff @righto.com · 23/03/2025

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

The keyset is an input device with five long, flat keys, similar to piano keys but thinner. The device and the keys are beige. A braided wire cord exits the device at the top.

An image from Engelbart's demo. At the top, the screen shows lines of text. The bottom of the image shows Engelbart at a special desk. The desk has a keyboard in the center with a keyset on the left and a mouse on the right.

526985

Ken Shirriff @righto.com · 15/03/2025

Happy Pi Day from a vintage IBM 1401 computer at the Computer History Museum (@computerhistory.bsky.social). This image is composed of the digits of π, printed on the 1403 line printer.

Line-printer output on green-bar paper. It shows a large pi symbol, made out of the digits of pi.

1707

Ken Shirriff @righto.com · 03/03/2025

Obscure electronics history: In this recent protest photo, why is the truck logo so similar to Fry's Electronics (which closed in 2021)? Answer: Fry's Food was founded in 1954 by Donald Fry and sold in 1972. His nephews founded Fry's Electronics with the proceeds. Thus, similar logos.

6545

Ken Shirriff @righto.com · 02/03/2025

Intel's Pentium processor (1993). Looking inside the chip , I found a large, complicated circuit just to multiply by 3 (lower right). Why? The Pentium uses a fast technique to multiply 64-bit number and it turns out that 3 is a special case. Let's take a closer look at multiplication... 1/N

A die photo of the Pentium processor. Under a microscope, the chip is a tan square with darker rectangular regions and tiny lines. I've removed a metal layer of the chip to make the circuitry more visible. The main functional units are labeled: caches, execution unit, floating point unit, microcode ROM, and so forth. A rectangular circuit in the lower right is highlighted: the times-3 circuit.

416734

Ken Shirriff @righto.com · 02/02/2025

The F-4 fighter plane used a three-axis attitude indicator to show the plane's orientation. (Like an artificial horizon with a third axis.) @curiousmarc.bsky.social, @tubetime.bsky.social, and I restored a damaged indicator. The video includes burning slip rings: www.youtube.com/watch?v=snP_...

youtube.com

ARU-11/A Attitude Indicator - Part 1: Tear Down and Release of Magic Smoke

YouTube video by CuriousMarc

2573