DEC Pro operating systems and MFM emulator

Paul Koning paulkoning at
Sat Jan 23 12:46:52 CST 2021

The question was asked (I misplaced the note) if the OS images that are on the Xhomer website work with David Gesswein's MFM emulator on real hardware.

You can turn these into emulator data files, provided you have the latest ext2emu tool that's part of David's software (as of 1/19/2021).  The format needed is "Elektronika_85" which is the Pro format, called that because it was first added to the emulator as the format found on the Russian bootleg copy of the Pro of that name.

Results, on my Pro 380:

1. P/OS 3.2: works.
2. Venix: panic at boot, "Bad access number".  That doesn't mean anything to me.  I wonder if the issue is that Venix doesn't support the 380.
3. RT-11 5.3: works.

For grins I tried a smaller interleave factor than the default 5:1, since it seems reasonable that this should make things go faster on the Pro 380, given that its CPU is about 4x the speed of the one in the Pro 350.  Somewhat to my surprise this isn't the case; the performance indicates that at 4:1 or smaller interleave the software misses the next sector and has to wait for another revolution.


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