30 Mar
2023
30 Mar
'23
6:24 p.m.
On 3/30/23 10:48, Fred Cisin via cctalk wrote:
The drives in many IBM PS/2 machines don't seem to
have a media sensor,
so they can't tell the difference between "720K" and "1.4M"
disks.
"720K" is about 600 Oersted, and "1.4M" is about 750 Oersted, so
they
are close enough that sometimes one can get away with using the wrong one.
Those PS/2 drives often have peculiar IBM-specific interfaces. For
example, some are 40 pin instead of 34. Or power is shared on the same
cable as signals, etc.
You're not likely to consider them.
There once existed single sided drives. Such as the
original Shugart
SA300 They were used in early Gavilans, but were replaceable with double
sided, especially the SA350, which could use the Gavilan's custom SA300
bezel,
Epson Geneva PX8 was 40 cylinders, intead of 80, with 67.5tpi, instead
of the usual 135tpi.>
The original Sony FULL height drives were at 600RPM, and had a different
interface.
The Tandy Portable Disk Drive, for the model 100, was weird and a half.
But none of those are high-density drives.
I'll add one of the issues may be drive-select setting for non-PC
devices. It's easy enough to get around, however.
--Chuck