29 Oct
2024
29 Oct
'24
noon
360K drives
(40 track) have tracks 48 tpi. (Early on, Shugart SA400, and
For the pedants, the IBM 360K format is 80 track. 40
cylinders, each
of 2 tracks, one on each side of the disk.
point taken.
I should have said "Tracks per side"
There were a few 100tpi 5.25" drives. Annoying
because they couldn't
read 40 cylinder disks even if you double-stepped them. Didn't
Commodore use them in the 8050?
Yes, but this was in response to 360K/1.2M issues.
I have had some 100TPI, both Micropolis and Tandon TM100-4M
One of the 100tpi Tandon drives is mislabeled as being TM100-4, without
the criticaally important 'M'
3.5" drives tend to be 80 cylinder, 135 tpi.
There were a few 40
cylinder 67.5 tpi drives with, I assume, a wider head. I've never seen
one in a PC though.
Not in s PC, but Epson Geneva PX-8 used one.
The spec I can find for the 40 cylinder 3" drive
says it's 100tpi. So
I assume the 80 cylinder one (often used as a second drive on Amstad
PCW's) would be 200tpi.
It is possible
to use a 1.2M drive to make a usable 360K disk,
Use the right ("360K"/300 Oersted) diskette. DO NOT USE A 1.2M DISKETTE!
Start with a thoroughly bulk eraased or virgin disk that is NOT "preformatted"
The 1.2M drive will have to "double step" to get 40 tracks at 48tpi
The drive must not be using the HD write current (I've no idea of amperage)
The drive must switch to 300 RPM at 250K bps, or switch to 300 bps at 360 RPM
The resulting diskette will have narrower tracks than normal, which is
usually not a problem, but the tracks will be at the right spacing.
I've done this many times, mostly to write 40 cylinder CP/M disks on
80 cylinder drives. I use a bulk-erased disk, format and write on the
80 cylinder drive then copy it to a fresh 40 cylinder disk on the
target machine. Never had any problems doing that.