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The DMAC can probably be removed from the machine config then. Can the owner confirm whether it has 80 track 5.25 floppy drives and if they are single or double sided?

let me say that you're doing a great job here!

Asked him. Note, this is a 'pc-in-a-keyboard' machine, so the drive was external.

Pics: http://ru-oldpc.livejournal.com/26180.html

The specs in that post say that cassette interface had motor control (other clones don't have that luxury).

Thanks. This clone is unique among others -- its video controller is almost, but not quite, entirely unlike CGA: it doesn't use a mc6845, always runs in graphics mode, but you still can set a text mode via standard CGA ports. Any access to those (and video memory in text mode) causes a NMI, and its service routine does the rest.

Fortunately, there is BIOS source (that doesn't quite match the binaries) and technical manual (for a pre-release hardware) and a set of schematics (for two different hardware revisions).

+1 for the Douglas Adams reference

Anyway, I love seeing news about these obscure Russian clones turning up recently. It's like a whole new world waiting to be uncovered (and emulated )

Oh yeah, there are at least two more PC clones unemulated:

- Istra-4816 -- triple-CPU (8086 + 2x8080), could run DOS and/or CP/M (concurrently). I have some of its software but no dumps. Wiki: http://ru.wikipedia.org/wiki/%D0%98%D1%81%D1%82%D1%80%D0%B0-4816
- Neuron I9.66 -- uses Multibus instead of ISA.

Before IBM PCs, there were others:

- Iskra 226 -- said to be a clone/reimplementation of Wang 2200
- Electronika D3-28 -- likewise, of Wang 720

This hardware is rare enough my now, but software is nowhere to be found; f.e. apparently there was a port of V7 UNIX to Iskra 226.

More WIP:

https://gist.github.com/shattered/5564625 softlist for mc1502
http://www.sendspace.com/file/990uey software

I had to hack wd_fdc.c, not sure how to do this cleaner. The reset routine (INT 13H AH=00) fails otherwise -- it waits for S_NRDY to clear and it never does.

How to use: press Enter twice after POST completes, at the '-' prompt enter '@'.

'ots' is a bad dump -- apparently the disk had 82 or more tracks, only 80 are dumped. It shows the logo, though.

'sfdos' is a good dump (it boots in ec1841), but doesn't boot here (fails to read 4 sectors starting at chs 0:1:6).

Try commenting line 112 of wd_fdc.c and see if that fixes it (it fixed it for me but with an MS-DOS floppy).

Apparently something changed in last two months, because the hack is no longer needed, but 'sfdos' still doesn't boot.

asst128's BIOS I uploaded is not original, it was modified twice (once by whoever designed the 3rd-party floppy interface, and then by the owner). Second change NOP's this block of code:

-000FE1EE: BA 01 01 mov dx,101h
-000FE1F1: E8 14 03 call 0FE508h
-000FE1F4: FA cli
-000FE1F5: F4 hlt