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Need help identifying which system these mystery cards go to and what they are!

VERAULT

VERAULT

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Jan 30, 2012
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Location
Connecticut, USA
I purchased these two cards very cheap because I had no idea what they are or what system they go to. They are both 72 pin card edge connector cards but vary in height. One has an SGS Z8420AB1 which is a serial controller chip I believe. That card as a 10 pin header at j1 and a single pin header just labeled "1" 2 inches below it. The second card has a WD FD1797B-02 which appears to be some floppy controller card even though this card has no card edge or headers for hooking up a cable. Detailed photos of front and back of cards can be seen here. Anyone care to make a guess? https://photos.app.goo.gl/pN4F8DRgChaaq9Cq7
 
Quite curious just how "anonymous" the cards are. Whatever the system, it would appear that it is designed to carry signals to external connectors (RS-232, Floppy) through the backplane, and so it is not a true bus in the sense of things like S-100. Each slot may have custom wiring and boards probably cannot just be placed in any slot. Also interesting how the serial board seems to create 220/330 resistor networks out of discrete resistors - perhaps it is not RS-232 but some other physical layer.
 
Would very well be. I was only speculating from what I can see on the board. I see a z80 serial IO chip and a 10 pin header seemed like Serial to me, but it could be something completely different sure. The fact that they dont have back plates and are much different in height is strange as well. Also the card edge with the floppy controller ship has a notch cut into it as the other does not.
 
Well, this clearly isn't for a standard bus system. The card with the SGS IC is likely a DAC sort of affair (the 40 pin IC is a Z80 PIO (Z8420 data sheet here), so simple parallel interface) and perhaps an R-2R converter. That's my 3 minute guess.
 
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That makes sense Al! The seller sold off two Xerox 820 systems. I think Im going to reach out to the seller and ask them to put me in contact with whomever bought those computers and see if they are missing or have a need for these cards.

It would still be good to know what each of these cards is/does.
 
durgadas311 said:
Interesting, this photo shows a system with the same Floppy card as yours: http://bitsavers.org/pdf/xerox/820-II/pictures/820-II_1.JPG, but that system has only one 72-pin slot, so could not also have the parallel-port card at the same time. Perhaps there were other models that had more slots and used the same cards, or there were practical applications that required no disk drives.
Click to expand...

Thats interesting. Thanks, I havent seen the board of a xerox 820. I know there were several models (800 series) so possibly some have more than the one 72 pin slot.
 
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