Ken Shirriff's blog

Computer history, restoring vintage computers, IC reverse engineering, and whatever

April 18 2026 · Edited Apr 18, 2026

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 from the positions of the stars, planets, or the sun. While celestial navigation is accurate,

by Ken Shirriff's blog

February 14 2026 · Edited Feb 14, 2026

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 8087 floating-point coprocessor chip. With this chip, CAD software, spreadsheets, flight simulators,

by Ken Shirriff's blog

November 23 2024 · Edited Feb 12, 2026

Antenna diodes in the Pentium processor

I was studying the silicon die of the Pentium processor and noticed some puzzling structures where signal lines were connected to the silicon substrate for no apparent reason. Two examples are in the