R-DOS (REX DOS??) on an oceanic 1541 clone drive

I picked up an oceanic 1541 disk drive clone in a recent haul of
Commodore stuff. It's actually branded "EXCELERATOR+PLUS", but it's an
Oceanic drive.
It has a DOS ROM I'm not familiar with, and has the
ID string "73,R-DOS 40 TR. 1541,00,00". Some googling has revealed
that some people have guessed it as "REX DOS" - but I can
find next-to nothing about it. ( I personally doubt it)

The drive itself works, and I've dumped the ROM using drvmon. It boots
up and works fine under VICE, and it can be found at
http://www.digitaltapestries.com/misc/rdos.bin
I plan to poke around in it, and see if I can reverse engineer the
command strings out of it, but that may take a while.

There seems to be a total lack of information about this DOS - in
particular I'm curious about the command strings to utilise the 40
track capability hinted in the ID string.

Does anyone have any info about this ROM?

In an unrelated query - I've been reviving a 1982  KU-14194HB
silver-label machine. It's now working fine (RF modulator was dead) but I'd love a schematic
for the thing, and I've been unable to locate one.  Has anyone seen
one?

Julian


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