1 Jul
2004
1 Jul
'04
4:41 p.m.
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.