SWTPC 6800 and Percom Floppy Controller

[deramp5113]

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?

Mike

 

[glitch]

I'll see what my LFD-400 has in it, it may not be immediately useful to you as it's installed in an Altair 680.

 

[deramp5113]

Great - I'd like to see what PROMs you have installed. For console I/O functions, the Percom PROMs call entry points in the computer's PROM monitor, so it shouldn't be hard to patch your PROMs to use SWTBUG entry points instead of those in the Altair 680 PROM.

Let me how your PROMs are labeled and maybe I'll want a dump. Thanks!

Mike

 

[glitch]

Well, they're labeled 1, 2, and 3 I'll dig into the docs and see if the previous owner noted what he was running. I have the full system, but haven't had time to dig into it.

 

[deramp5113]

I’ve been able to complete the system running under the MiniDisk+ PROMs and added several programs like BASIC and an assembler to the disk. It all works together, but operations don’t integrate with each other very well.

I also obtained the source to Percom’s MPX PROM, so I was able to create a system running under MPX. The hobbyist who had the MPX source also had several of the programs (in S19 format) that would have been distributed with MPX, so I’ve got a pretty representative Percom MPX system up and running now. This setup, in turn, is pretty darn slick and well integrated for its day. It’s a lot like a Northstar DOS system, but a bootable disk is not required to get started since the OS is in PROM. Add the fact that the standard SWTPC configuration with MIKBUG or SWTBUG made it simple to get programs into RAM via the serial port (e.g., S19 records from papertape, cassette, or today - a PC) and it’s easy to build up a disk from scratch.

I’d still like to flesh this system out a bit more, so if anyone has any Percom disks or software archived in any format on a PC, let me know, thanks!

Mike

 

[deramp5113]

I have typed in the assembly source for couple of the missing utilities I was looking for (there are a few listings in the LFD-400 manual), so I now have a pretty complete and useful Percom disk system for the SWTPC 6800. I also wrote FLOP2PC and PC2FLOP utilities to archive a disk to a PC and to write a disk from an archived image saved on a PC. The disk images are transferred over a serial port using the XMODEM protocol.

Mike