Post #1974726

2026-05-03 15:21 UTC

Ok, so finding a printable version of the PCB and overlaying it on a lightbox gives the attached. This seems pretty clear to me that not only are (what I know as) D0 on both 16-way connectors connected, but they are also both connected to input side 2A1 and output side 1Y4 of the same 74LS244. I think I have to at this point conclude that the schematic is wrong...

Replies (4)

@diyelectromusic@mastodon.social 2026-05-04 15:47

So having traced through the PDS PC card PCB at a high level the connections are, I believe, essentially as shown here in this "pseudo schematic". Of course, I'm assuming the PCB actually works :)

Open ##1974727
@scruss@xoxo.zone 2026-05-03 16:01

@diyelectromusic developed by Andy Glaister, originally running on an Apricot. The dev system of choice for well-heeled games companies: https://www.glaister.com/History/Andy/Andy%20History.htm

Open ##1974731
@RueNahcMohr@infosec.exchange 2026-05-03 16:21

@diyelectromusic I might do that for a bi-directional data bus...

Open ##1974734
@bytex64@awesome.garden 2026-05-04 01:37

@diyelectromusic Yeah, I see what you mean. It only looks like half of these 244's are even used, like the card is implementing only one port but connecting the signals to both? Very strange. Very interesting that this originally used an Apricot PC (and annoyed to see it referred to as a "PC clone" - it was a different architecture!). Too bad none of the original hardware or software seems to have survived for it. It would have been very cool to try it on mine.

Open ##1974736