I have the MP-A2 board in a SWTPC 6800 machine.
I can put the schematic and some documentation about it (memory map, config switches) up on the web if you wish.
The 4 right-most sockets are for 2716 ROMs which can be variously switched into upper memory with all those config switches. The left-most socket of the 5 normally contains the monitor (mask-programmed PROM, mine is labeled SWTBUG-1.0, which, IIRC, is a modified version of Motorola's MIKBUG, actually it may have both SWTBUG and MIKBUG burned into it).
If there is a 6810 to the left of the ROM sockets, that's a 128 byte RAM.
The 6875 is a clock/reset generator for the 6800, the CPU clock is RC, not crystal.
The crystal and MC14411 are for baud rate generation, nothing to do with the CPU, they just supply a common set of baud rate clocks to the bus so multiple I/O boards don't have to each have their own.
It's almost a single-board computer. If that's the SWT or MIKBUG monitor in ROM then it needs an external 6820 PIA with a little glue and interface logic to connect to an RS-232 terminal (the monitor does parallel/serial conversion in software).
Jules Richardson wrote:
> One of the things I found in the heap was a SWTPC CPU board. I know
> nothing about them, but it looked interesting enough to be worth saving
> from an unknown fate.
>
> However, the board's different to the one at:
>
> http://www.computercloset.org/SWTPC6800.htm
>
> This one has 5 larger IC sockets along the top edge, the leftmost of
> which is populated. there are two 7805 regulators toward the centre of
> the board at the bottom.
>
> Bus is 50 pins, just like the card in the above photo - SW-50 I guess.
>
> There was no sign of a case for the board, backplane, or any other cards
> though.
>
> Anyone know what the different board variations are? This one says
> "MP-A2" in the top right corner along with a copyright symbol.
>
> Build date looks to be mid-to-late 1977.
Received on Thu Jul 01 2004 - 20:41:38 BST