Milwaukee Computers MC-1200

Al Kossow aek at
Mon Sep 3 09:58:38 CDT 2018

Another small project off my plate.

Ethan had asked me years ago to make copies of the software for this machine.
It is pretty obscure, one full page add in Byte, and it sank without a trace.

6502, p-System, totally custom MFM-encoded floppy interface based on a Moto 6852
synchronous serial interface chip.

I had bought a Supercard Pro a while ago, and set it up to do some hard-sectored
floppy imaging. Figured this would be a good test case, since it didn't have the
problems with dealing with out of sync data streams (the SCP doesn't grok more
than one sector hole so you have to turn off index synchronization).

Made images, dragged my machine out of storage, cleaned it up, made a clone from
the SCP image, and it booted! yay!

SCP images are up under

I also put up cleaner images of the schematic and board layout, and annotated a
disassembly of the boot prom from a scanned listing i've had for a while under

One thing I noticed that made me nervous is looking at the code there is no
checksum on either the sector address or data fields on the floppy. I made an
image of a floppy that I bulk-erased and initialized this morning, and all you
see are the sync bytes and data, no trailing data where a crc would be.

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