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righto.com
Computer history. Reverse-engineering old chips. Restored Apollo Guidance Computer, Alto. Ex-Google, Sun, Msft. So-called boffin.
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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

submitted 4 days ago • 2 comments

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

submitted 19 days ago • 11 comments

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.

submitted 28 days ago • 1 comment

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.

submitted 32 days ago • 2 comments

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

submitted 33 days ago • 3 comments

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

submitted 39 days ago • 2 comments

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

submitted 48 days ago • 3 comments

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

submitted 55 days ago • 1 comment