> We're teaching 2020s engineers to understand machine code written before MS-DOS existed
It has three on-board computers. Two of them (the CCS and AACS) are 18-bit word-oriented machines with 4096 words of memory – so in 8 bit bytes thats 9KB of RAM. Although 18-bit machines were reasonably common in the 1960s and 1970s (especially the DEC PDP-7 which was the birthplace of both UNIX and MUMPS, its predecessor the PDP-4 and its successors the PDP-9 and PDP-15), you'd never encounter them nowadays except in retrocomputing or ultra-legacy systems like this. The other one (FDS) is a 16-bit word oriented machine with 8198 words of memory – so a bit less esoteric, although the 16-bit systems most people would be familiar with (e.g. the Intel 8086/8088 used by MS-DOS) are byte-oriented not word-oriented. So yeah, even for people used to doing assembly programming, might take a bit of time to get your head around it.
Both computer architectures are NASA custom, not industry standard – although they were reused from the Viking Mars landers, so weren't a brand new thing to NASA at the time. Rather than a single chip CPU, their CPUs were built out of a large number of 7400 series TTL ICs – so essentially early third generation computers (small scale integration, SSI, became available in mid-1960s), as opposed to fourth generation computers (1970s, with LSI/VLSI, transistor counts on integrated circuits had become high enough that the whole CPU could fit on a whole microprocessor).
(There is this widely repeated legend that the Voyagers used RCA 1802 CPUs, but that appears to be mixing up Viking/Voyager which used NASA custom CPU architectures, with the Galileo probe launched in 1989, which used RCA 1802 CPUs for its main computer, plus Itek ATAC CPUs for the attitude control computers. The ATACs were also used by some US naval aircraft – and whereas the Voyager was all assembler, the Galileo ATAC CPUs were programmed using HAL/S, the same language used for the Space Shuttle flight software.)
> although they were reused from the Viking Mars landers
Correction: the 18-bit computers used on the Voyagers were reused from the Viking orbiters. The Viking landers used a different computer architecture, the Honeywell HDC 402, which used a 24-bit word, and was not reused by Voyager
It has three on-board computers. Two of them (the CCS and AACS) are 18-bit word-oriented machines with 4096 words of memory – so in 8 bit bytes thats 9KB of RAM. Although 18-bit machines were reasonably common in the 1960s and 1970s (especially the DEC PDP-7 which was the birthplace of both UNIX and MUMPS, its predecessor the PDP-4 and its successors the PDP-9 and PDP-15), you'd never encounter them nowadays except in retrocomputing or ultra-legacy systems like this. The other one (FDS) is a 16-bit word oriented machine with 8198 words of memory – so a bit less esoteric, although the 16-bit systems most people would be familiar with (e.g. the Intel 8086/8088 used by MS-DOS) are byte-oriented not word-oriented. So yeah, even for people used to doing assembly programming, might take a bit of time to get your head around it.
Both computer architectures are NASA custom, not industry standard – although they were reused from the Viking Mars landers, so weren't a brand new thing to NASA at the time. Rather than a single chip CPU, their CPUs were built out of a large number of 7400 series TTL ICs – so essentially early third generation computers (small scale integration, SSI, became available in mid-1960s), as opposed to fourth generation computers (1970s, with LSI/VLSI, transistor counts on integrated circuits had become high enough that the whole CPU could fit on a whole microprocessor).
(There is this widely repeated legend that the Voyagers used RCA 1802 CPUs, but that appears to be mixing up Viking/Voyager which used NASA custom CPU architectures, with the Galileo probe launched in 1989, which used RCA 1802 CPUs for its main computer, plus Itek ATAC CPUs for the attitude control computers. The ATACs were also used by some US naval aircraft – and whereas the Voyager was all assembler, the Galileo ATAC CPUs were programmed using HAL/S, the same language used for the Space Shuttle flight software.)