SWTPC 6800 and Percom Floppy Controller

William Sudbrink wh.sudbrink at verizon.net
Wed Jan 8 10:31:51 CST 2020

You might try asking on the Flex Users "fufu" list.  I have a working MiniDOS PlusX LFD-400 setup.  I would be happy to trade dumps if you are interested.

Bill S.

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Mike Douglas via cctalk
Sent: Tuesday, January 07, 2020 7:45 PM
To: cctalk at classiccmp.org
Subject: SWTPC 6800 and Percom Floppy Controller

I’m restoring a SWTPC 6800 that includes the Percom LFD-400 floppy controller. This controller goes on the SS-50 bus instead of the SS-30 bus where the SWTPC controllers installed. The standard Percom MiniDOS PROM is installed, and the other two PROM sockets have a third party extension called “Minidisk+”. This was made by a company called Cer-Comp. These PROMs are instead of Percom’s own “MiniDOS PlusX (MPX) PROM. 

I’ve got the system working, and I can use Minidisk+ to save and load files, but I know I’m missing some nuances of command parameters. I don’t have any sort of documentation for Minidisk+, so before I go figure it out by disassembling the PROMs, does anyone have any sort of documentation for Minidisk+ by Cer-Comp for the Percom LFD-400 floppy disk controller?

Also, I’d like to burn the MPX PROM as an option. Does anyone have the MPX PROM or the source code for MiniDOS PlusX?


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