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Comment by Luc | Hacker News Reader

The conclusion seems a bit strange.

Why does the Soyuz clock contain over 100 chips instead of being implemented with a single clock chip? Soviet integrated circuit technology was about 8 years behind American technology, so TTL chips were a reasonable choice at the time.

Because in the paragraph above:

I expected the Shuttle computer to use 1980s microprocessors and be a generation ahead of the Soyuz clock, but instead the two systems both use TTL technology, and in many cases almost identical chips.

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The point is that the Shuttle's TTL chips were more advanced as far as performance, using Fairchild's FAST line. The Shuttle also used many TTL chips that were more complex. This is consistent with the CIA's claim that American ICs were 8 to 9 years ahead. But it's interesting that the Shuttle was still using TTL, and many of the chips were very basic, like the quad NAND gate chip. So the difference between the two boards was surprisingly incremental, rather than a jump to MOS chips or microprocessors.

> The point is that the Shuttle's TTL chips were more advanced as far as performance, using Fairchild's FAST line.

This. The author points out the 54F00, seemingly distracted by the 54'00 part and similarities in TTL glue logic layout that the F part is completely dismissed without acknowledging that these chips had sub-4ns edge rates and were indeed fast while remaining compatible with older TTL families. Throw in high SMD density on a multi-layer controlled-impedance PCB designed to survive brutal operating environments when PCs and CAD were still in their infancy...even today, it's humbling to contemplate just how much work would have been required to qualify such a design.

> But it's interesting that the Shuttle was still using TTL...

These systems had super long lifecycles and were required to be extremely reliable. I'd be surprised if the contractor that was responsible for the design would have been allowed to integrate any IC that wasn't listed in a QML.

FYI, that’s the author you’re talking to.

Hadn't realized; thanks for pointing that out.

I recall as a kid seeing in electronics magazines in the late 70s some ads about a clock kit everyone could solder in a evening thanks to a then new module called MA1001. Some searches confirmed it was introduced in the mid 70s.

It was way behind yes (and much of it was ripped off, China-style, from Western designs), but I agree it's weird to compare a _computer_ with a _clock_.

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