On December 16, 2018 at 11:14 PM allison via cctalk <[email protected]>
wrote:
On Sun, 16 Dec 2018, Norbert Kehrer via cctalk wrote:
I have not tested it, but I suppose, that also the PX-8 and PX-4 used
the protocol,
because the protocol specification defines the following device numbers:
- HX-20: 0x20 (probably also used for the HC-20)
- PX-8: 0x22
- PX-4: 0x23
PX-8!
A subject dear to me. I still have the px-8 I bought new (borrowed the money
from my sister) as a young man in 1984. Alas, I could never afford the PF-10
disk drive.
However, the PX-8 3.5" had 40 cylinders, with 67.5 tpi, instead of the
common 80 cylinder 135 tpi of other 3.5" disks.
Those 40 cylinder 3.5" drives are quite rare.
On Sun, 16 Dec 2018, Will Cooke via cctalk wrote:
Somewhere in my searches I recall reading that the 3 1/2" drives used
the same format as the 5 1/4" ones. Maybe 40 tracks of 16 256 byte
sectors. Oddly, I believe that 2 tracks are "reserved for CP/M" even
though it is in ROM and not stored on disk.
It was not uncommon for CP/M disks to have "reserved" or "system" tracks,
even when the particular disk was not a bootable "system" disk.
I don't remember for sure, and don't have convenient access to my
materials, but 16 256 byte physical sectors makes sense.
The drive manual
http://electrickery.xs4all.nl/comp/px8/doc/PF-10Manual.pdf
SAYS 9 512 byte sectors, but that seems likely to be in error from a cut
and paste boilerplate from a different machine, because the more specific
information is all for "64 sectors", which means CP/M RECORDS or "logical
sectors" of 128 bytes each. THAT would be consistent with either 8 512
byte PHYSICAL sectors, or 16 256 byte PHYSICAL sectors.
--
Grumpy Ol' Fred [email protected]
