Next up I'll implement the ROM switching. That will at least make it go to MSX-DOS or disk basic.
Done! And indeed, it's nicely booting up MSX-DOS when no CP/M disk is found 
To actually run CP/M disks I have to extend support for other formats in openMSX. It doesn't currently support such formats (40 tracks/side, 17 sectors/track and 256 bytes/sector), it seems.
So, this is next on my list... but support for CP/M disks for diskmanipulator and dir-as-dsk is out of the question for now, folks...
- on the MSX-DOS disk there is the program "RAMDISK.COM", which also seems to write to the ROM swap registers.
Does someone know more about this program? How does it work? It seems it needs a 64kB RAM expansion (according to the SVI-707 manual), but I can't find anything more about it. It seems to contain a diskROM in itself...! Anyway, I still couldn't get this one working, the SVI-728 hung up when I ran it, even with a 64k RAM module in the cartridge slot.
Any ideas what could be wrong?
I found out the following (I connected the SVI-707 to slot 3 and put a 64kB RAM cart in slot 2):
- Before it resets the MSX (with an explicit jump to 0x0000) it copies a large block to slot 2 where the RAM is, at #3000; actually several ldir routines from 0xD000 apparently do copies like that, with different slot configurations (0x55, 0x5a, 0x50 in I/O port 0xA8)
- when debugging I found out it copied a diskROM to page 1 of the slot 2 (the extra RAM slot) and what looks like a boot sector to 0x3000
- at the point where it crashes, there is indeed that diskROM present and slot 2 is in page 1 (so the copied diskROM is active). Page 2 and 3 contain the normal RAM from slot 1 though. It crashes because it does a ret at 0D11 (is that the end of the interrupt routine?) but the stack has 0x7C87, so it ends up in uninitialized memory of slot 1... 
and there is where I gave up
If someone wants to help to debug, please use the latest openMSX build and use the new ram64k and Spectravideo _SVI-707 extensions. The CP/M ROM is the one that mars mentioned, but only the first 4kB.
Some good news: I managed to convert the CP/M DSK file into a DMK file and with that I see CP/M booting fine So the SVI-707 emulation seems pretty good now, except for that issue with 'RAMDISK' which I mentioned above. I hope someone can help there.
Look at the demo video I just made https://www.youtube.com/watch?v=6x5YIa4vQdQ
