16 Dec
2018
16 Dec
'18
8:56 p.m.
On December 16, 2018 at 11:14 PM allison via cctalk
<cctalk at classiccmp.org> wrote:
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:
On Sun, 16 Dec 2018, Norbert Kehrer via cctalk
wrote:
PX-8!
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
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 cisin at xenosoft.com