On 1/9/23 22:31, Fred Cisin wrote:
>
> 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)
What Fred said. I'll add that a similar situation applies in the 3.5"
world. The standard in the Japanese NEC PC world was for all floppies
to share a common format, namely 8 sectors of 1024 bytes, starting with
the 8" drives, which normally spin at 360 RPM and use a 500Kb/sec data
transfer rate. So the IBM 5170 1.2MB drive in high-density is a direct
descendant of that, though early Japanese 1.2MB drives did not have a
low-density mode--and IBM elected to stick with 512 byte sectors.
Finally, we get to 3.5", where the NEC standard was 360 RPM, not 300.
This resulted in the "3-mode drive" where a pin (usually pin 4) is used
to switch the drive RPM between 300 and 360. The Teac FD235HG drives
can do this (assuming that they're jumpered correspondingly). The 1.23
MB format was used on a lot of Japanese CNC gear; e.g. Mitsubishi/Mazak.
--Chuck
