Looking for SMD drives (specific models)
jws at jwsss.com
Sun Apr 12 20:48:59 CDT 2015
On 4/12/2015 5:05 PM, Jules Richardson wrote:
(actually Josh wrote this)
> I have a few other SMD drives (just picked 'em up today, in fact) but
> they're newer (~825mb) and the Ridge disc utilities only support a small
> subset of drives (they do not support providing custom geometries,
> that would be *too easy*.)
The larger drives have more bits / track than the ones you have in the
list. I suspect the 825mb and so forth may have too high a bit frequency
for the ECC or CRC generation hardware in the controller.
I don't recall the number of bits / track, but there were a couple of
generations with about 20k / track, the 9766 was in that class. Then
later there were drives which were twice that.
The part we used to compute CRC for our drive at the time could not
handle the frequency of the 40k tracks. And the parts for ECC were not
mature to change to that technology, so we never supported the EMD (40k)
I have a CDC 160mb MMD which is probably compatible with the system you
have. I believe the Ridge was out when we did our controllers.
As to Jules's other mention, about the parameters, CDC recorded a well
documented block of data on the first track with flaw map information.
There are no drive parameters for SMD. We had a rom with a number of
geometries, as well as some table with block capacities which were
reported to the Reality OS for it to use the drive. Our interface was
at a block count level, not a CHS layout level.
The place to attack Ridge would be to look for the tables for the drives
that Josh has in his list in the disk controller roms, and attempt to
modify that table. That would assume one could modify that table, and
there no protection on the rom such as a checksum that would mess up if
you diddled the table.
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