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Comment by jdblair | Hacker News Reader

If you want to learn about how the Voyager flight data system is designed, read Nasa's historical document Chapter 6: Distributed Computing On Board Voyager and Galileo [1].

The whole read is gripping, but the most interesting part for me is the section "Developing Voyager's Flight Data System Computer " describes the choice to use CMOS memory and DMA from instruments.

[1] https://history.nasa.gov/computers/Ch6-2.html

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It was a different world in 1975:

  After determining requirements, Wooddell examined possible hardware and software tradeoffs. In an insightful memorandum, John Morecroft explained the concept of "soft logic" as a complement to the "hard logic" in the Flight Data System44. Writing in 1975, when the actual flight software began to be prepared, Morecroft pointed out that the program for the computer was actually a soft representation of hard-wired circuits. Conceptually, the memo stands as an explanation of the essential meaning of firmware in general.

Damn, that's cool. Do you have a link to the whole document?

To the memorandum? No! That would be fun to track down.

Looks like this, although a quick search doesn’t find it:

43. J. Wooddell, "Design of a CMOS Processor," pp. 2-3, files of J. Wooddell. 44)J. Morecroft to K. Frewing, "FDS Programming," January 14, 1975, files of R.J. Rice, Jet Propulsion Lab.

Contents [0]

Part I : Manned Spacecraft Computers [1]

Part II: Computers On Board Unmanned Spacecraft [2]

Part III: Ground Based Computers for Space Flight Operations [3]

[0] https://history.nasa.gov/computers/contents.html

[1] https://history.nasa.gov/computers/Part1.html

[2] https://history.nasa.gov/computers/Part2.html

[3] https://history.nasa.gov/computers/Part3.html

I just realized, there's an "index page" linked at the bottom of your OP's link. I didn't notice it initially.

https://history.nasa.gov/computers/contents.html

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