OT: Apollo Core Rope Memory

[gene heskett]

On 11/1/23 04:21, Jeffrey Walton wrote:
> If anyone is interested in hardware and software used on the Apollo
> missions to the moon, checkout this video:
> <https://www.youtube.com/watch?v=hckwxq8rnr0>.
> 
> It is fascinating how the folks are recovering the original programs
> for the flight computers. (Many of the programs have been lost to
> history).
> 
> Jeff

I have read several times that the microprocessor used there was the 
original RCA 1802 because as a cmos design, it was automatically rad hard.

I have worked with in 1978, wrote a program and made most of the 
supporting electronics with an eye to eliminating a dub copy to make the 
use it on air commercials that worked with an automatic station break 
machine. So useful that it was still in daily use by that tv station 
when I last checked in 1997. The RCA 1802 had an unusual architecture 
that had 16, 16 bit accumulators, any one of which could be the stack 
pointer and any one of which could be the program counter. An 8 bit data 
buss and a 16 bit address bus. Each controllable by a single 8 bit 
instruction byte followed by a target byte. 50 years later I still think 
it was a good architecture. I still have a big manilla bag with a paper 
copy of that program in hex codes and two broadcast audio carts with 
backups of that program on an upper shelf of the bookcases that line 
this room.  To save memory, I used self modifying code because 4k of 
static ram was then $400 on an s-100 board I had to build from a kit.
I paid attention to resetting all the modified instructions at the end 
of the program loop and it ran w/o crashing from power failure that 
outlasted a standby battery to the next long power failure. Rock solid 
stable. Wasn't fast, took 1270 microseconds to make one pass thru the 
loop. Up until Jeffrey posted this link, I had no idea what sort of 
memory was used by Apollo, thanks Jeffrey.

Cheers, Gene Heskett.
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