OKI if800 CP/M

[Jason T]

Does anyone have, or has anyone used, one of these machines?
Specifically the M10/M20 models, with 5.25" disks?

I have a vendor box here with manual and CP/M 2.2 boot disk for the
if800 and I've been trying to make a usable[1] image of the disk,
currently with the Kryoflux and their dtc conversion tool.  I sent the
flux reads of the disk off to the KF team and they found it
interesting enough to study, but there is precious little
documentation out there about this machine, much less its disk format.

Looking at the scatter plots of the magnetic flux on the disk, I can
see that it's 40 track and double sided.  Converting the dump to a
DS/DD MFM disk image yields many warnings and errors, but also a file
with plenty of discernible strings, so that's at least on the right
track. Images of reads of the two sides done separately show
alternating fragments of the strings of the full read, telling me that
it is a contiguous volume using both sides and not two single-sided
volumes.

One ad I found (mostly in Japanese,) suggests that the if800 drives
are 280K.  That's an odd number (to me) for a 5.25" disk.

-j

[1] I have neither the real machine nor an emulator to use them, so
this is mostly just an academic exercise in learning about disk
formats and disk imaging, for now.  But AIUI, if the disk's attributes
are known, it should be browsable with a tool like cpmls from the
CPMTools package.