What I have done so far with the SWTPC 6800-based S50 system:
Found Mike Holley's great site on the swtpc stuff,
without which I would have no progress to report.
ID'd all of the various cards, except one. Three 8K
SRAM cards. One newer 64K card which seems to be configured
to conflict with the other cards, so I am not sure it was ever
used in this system. Only has 8K installed, even though
that one card could replace all three of the others, which
are spec'ed to draw 1.5A each! I worked on the terminal first.
It didn't really need much. I added a DB-25 instead of the
ugly molex serial connector. (shielded cable for a serial
connection?) Did the same thing on the computer end.
Both cases already had holes for the DB-25, so it seemed
like a natural. Got the CPU card and one RAM card talking to
the terminal, after a little contact cleaning and resoldering
a few connections. The connectors are not gold, and are not
edge connectors, but fat pins on the MB and sockets on the
cards. They require an incredible amount of force to plug on,
so I added some extra support under the MB to keep it from
flexing too much. Was afraid it might get damaged. I added
a second RAM card, for 16K total. Keyed in a simple assy RAM
test which didn't find any errors. Downloaded 8K SWTPC BASIC
image from the web, and loaded it using the built-in monitor
program and a terminal program on a laptop.
Was able to type in a simple BASIC program and run it. (No
manual, so it took a little fiddling to figure out how to even do
that) I am trying to write a little assy program to fill the
terminal screen with some text for a static demo. Not working yet.
Without a floppy drive, this system seems rather limited.
I have not played with the cassette interface. Read that it is
really slow. Runs at 300 baud. Woohoo!
The serial baud rates are crystal-generated, but the CPU clock
is controlled by an RC network. Previous owner replaced fixed
R with a pot, so I can change the system operating speed with a
potentiometer! 1 MHz is the nominal CPU clock. (Similar to Apple ][)
--- billdeg <billdeg@...
> In addition to the museum room renovations, we also make progress
> some computer restorations
> 1) Bob Grieb has reported progress with the MARCH SWTPc 6800, SWTPc
> terminal and cassette interface. I assume he'll let us know how it's
> going in more detail soon. He is working on this unit at his home.
> 2) Using the the MARCH Altair 8800 as a control unit, Bob Grieb and
> Dan Ragonti did some comparative diagnostics on my Altair 8800. It
> was productive to have two Altair 8800s to work on at the same time.
> I took a lot of notes and will post them on my web site soon. Dan
> ended up taking my Altair home with him for further study/fun. The
> next day Nick (donated the MARCH Altair), me, and Dan a terminal
> working with the MARCH Altair. (I brought a Teleray terminal for
> testing) The MARCH Altair has CUTTER and the Subsystem B card from
> Processor Tech. To-do - get a terminal for the MARCH Altair.
> 3) We have about 6 Apple ][e / Plus computers. We were able to get
> least one complete working system. To-do - test all Apple ]['s plus
> the Apple //c, and //GS
> 4) The original version IBM PC 5150 - After taking apart the system I
> determined that there was at least one bad RAM chip in bank 1. It's
> 64K Unit with an additional 64K RAM card - 128K. This 5150 is the
> first version with the black power supply, very rare. I hope to
> restore before September. Note - we have the original boxes, monitor
> and keyboard, DOS 1.1, etc. Very nice.
> 5) DEC - No work done other than take a peek at everything.
> 6) Other stuff - Waiting for future...
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