On Sat, 17 Jul 2010, Chuck Guzis wrote:
On 16 Jul 2010 at 16:52, Steven Hirsch wrote:
That makes sense, but I'm wondering how they
dealt with that at the
software level. Under Apple DOS, you access disks by Sn,Dn (slot 1-7
and drive 1 or 2). Unless they patched DOS you couldn't say, for
example, S7,D4. I think I need to get the software for this beast.
Do you recall anything about the command structure?
No I don't, sorry. Does anyone still have one of the Corvus units
that use an IMI hard drive? ISTR that it mapped the drive into 50 or
floppies. Perhaps that might give some insight.
Ok, I think I see what they're doing. The driver patches Apple DOS to
expect a large logical geometry and maps logical track + sector requests
to physical diskette + track + sector. I expect it shuffles diskettes as
you exceed maximum block offset for a currently loaded disk.
At the hardware interface level, it's probably using binary select lines
to choose disk 0-4 from the cartridge.
Good news is that the unit booted into Vista DOS 3.3 when connected to my
IIe in the shop. The bad news is that it only did so once :-(. On
subsequent attempts, it sits and re-seeks endlessly. I suspect the media
is deteriorating and crapped the head up with oxide. I'll clean it up and
take a last crack at copying off the system software and utilities.
Next step is to take an X-acto knife to a handful of 5.25" 1.2M diskettes
and see if the loader can work with them.
I pulled down a copy of their patent application for the unit and it
almost looks like the Minipac diskettes have some sort of pre-written
servo track. Perhaps the unit can actually write this servo, but without
documentation I'm just surmising.
Steve
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