On 1/9/23 21:16, nico de jong via cctalk wrote:
Hello Chuck
Speaking of old floppies, when I was busy converting floppies (I've
now been retired for 10 years) I frequently had problems reading some
5.25" disks, but only on specific drives. Those disks came from IBM
systems, probably S/3.
I cannot be sure that the solution holds, but it was my experience
that those "faulty" discs could be read on TEAC FD235GFR drives
orignating from Japan. Not the ones from the Philippines ! That
puzzled me, until I called MIchael Cotgrove from (then) Intermedia in
the UK, who told me that he knew that some IBM systems ran the drives
at a lower speed, and that that very well could be the problem. After
that explanation, I only used the 142U version of the drive, and the
problems went away.
Does this sound familiar?
On Mon, 9 Jan 2023, Chuck Guzis via cctalk wrote:
HI Nico,
It sounds puzzling to me--the FD235 is a 3.5" drive, so I'm not sure
what you were using to read the problem disks with.
A little quick speculation, but not determinable without the system, . . .
The Teac FD55F was a 96tpi "720K" drive at 300 RPM
The Teac FD55G was a "1.2M" drive. 360RPM
The FD55GF was both, and there were several variants, with different
jumpers, etc. (hence differences between the various ones)
Was the drive running at 300RPM, or 360RPM?
If the disks were HD, then they should have been at 360 RPM, with a data
transfer rate of 500K.
If the disks were NOT HD, and were 640K - 800K "quad" density, then they
should have been at 300RPM with 250K data transfer rate, OR at 360RPM with
a 300K data transfer rate.
Could you have been suffering from something as simple as a rotation
speed / data transfer rate mismatch?
The 5170 supported 250K data transfer rates ("360K" disk/drive)
500K data transfer rate ("1.2M" disk/drive)
and 300K data transfer rate ("360K" disk in "1.2M" drive)
--
Grumpy Ol' Fred ci...@xenosoft.com
