OK, so I finally broke down and got my PET 8032 out of storage. It's been put away for years with no power. And naturally, it's dirty.

Anyway, I'm cleaning it up a bit and discovered two boards installed that are puzzling. One of them has a 6502 installed. The board had what looks like a custom cable (DB25) as you can see below. The board plugged into a socket on the main board at UB14 (between a 6545 and a 6522). I don't have the schematics at the moment but I will see if I can find them online.

My guess is that this was some kind of printer or disk controller. Any ideas?

The second board really doesn't have anything much on it but goes out to a circular plug in the back. There are some wires soldered directly to an expansion header. It really looks like it was made by an amateur. The first board MIGHT have been a commercial product. It's serial number 96.

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Cat; the other white meat.

Network?

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Do you mean on the first board or the second? The second (with the circular connector) might have gone to a token ring network perhaps?

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Cat; the other white meat.

OK, I'm stupid. I figured out what it is. It's the main 6502!!!

When looking over the board, I read a "6520" as a "6502" and assumed the CPU was on the main board. But apparently, it is not. Which is really odd. So I'm at a loss why it was designed that way. Especially since that little daughter card has a cable just dangling out the back.


**EDIT**

Wait, I bet the CPU was originally designed on the main board and this board just moves the CPU to the daughter card and adds some I/O or something.

I really don't know if I will keep it that way because I actually don't like that custom DB25 cable coming out the back. I don't really have a use for that. I wonder if I can just put the 6502 back in the original socket?

Now where's that schematic????

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Cat; the other white meat.

RS232 ?
6850 ACIA and 1488/9 level shifters wouldn't be out of place for a serial board, nor would that DB25

I'm really starting to think that's what it was for. A "cleaner" way of adding RS-232 without having to use one of the board's edge connectors. But, I really don't like that cable just dangling out the back like that. I think this was some aftermarket board.

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Cat; the other white meat.

The DB-25 connector definitely looks like RS-232 (pin 20 is ground, pins 2-8 used, others not populated) and the circuitry matches that guess.

I forgot what the name is of the round plug but I have a video monitor with those. They are also used for things like CB antennas. I suppose it could be a composite video output (e.g. for use in a class room) but I can't tell for sure from the pictures.

===Jac

That's a good guess. In fact, I believe the PET has an external pin for video out and the PET was used in many classrooms.

But, doesn't matter now...since my PET is fried (well, the monitor is).

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Cat; the other white meat.