Examining circuit boards from the Space Shuttle's I/O Processor

kens

Author here if you have questions...

ck2

oh that is absolutely fascinating to see in detail I wonder if the very low density (relatively speaking to today) make them more robust against gamma-rays and other radiation problems once outside the atmosphere? if I remember correctly, and it's been decades of course four of the computers ran in parallel with the exact same instructions in case one failed or came up with a wrong answer and the fifth computer was the "decider" is that understanding correct? ah I see now you mention Eight networks were assigned to flight-critical systems, with each CRT display and engine controller connected to four networks for redundancy.

elzbardico

Glass capacitors!!!! I didn't even know this existed! and made by Corning!

raphlinus

The description of the BCE reminds me a lot of the PIO in the RP2040 and 2350 microcontrollers. From the article, BCE instructions include "Transmit Data, Receive Data, Load Timeout Register, Store Status, and Wait." To me, these correspond more or less 1:1 with PIO instructions OUT, IN, SET, INT, and WAIT. These plus PUSH, PULL (which can considered auxiliaries of IN and OUT), MOV, and JMP are all the PIO instructions. Like the BCE, it runs with completely deterministic clocking, one instruction per clock, and like the BCE there are a bunch of them (a total of 12 state machines on the 2350), though they now run totally in parallel rather than being time-multiplexed. As a hobby project, I've lately been implementing USB (aiming for higher performance than Pico-PIO-USB, which proves that it's possible), and that's been quite fun. I wonder to what extent they were explicitly inspired, and to what extent you just get convergent solutions when there are similar goals and constraints.