15 Sep
2013
15 Sep
'13
3:56 p.m.
On Sun, 15 Sep 2013, Chuck Guzis wrote:
On 09/15/2013 01:26 PM, Fred Cisin wrote:
Another thing that tends to bite people with NEC (and clone) PC98
machines' floppy drives is that they almost all use a true Shugart
interface (even for 3.5" drives!) and not the bastardized "simplified"
IBM-PC compatible interface that became so common due to the IBM PC/AT.
They may have the same number of pins on the connectors, but they are not
/exactly/ pin-compatible. You can't simply plug a common IBM-PC compatible
drive into an NEC PC98 machine and expect it to work (it won't). When
dealing with these, the best "fix" is to clean and align the existing
drive, but the alternative is to find one of the somewhat rare drives that
can be set to function as true a Shugart compatible drive (changing just
one or two of the signals doesn't cut it with NEC PC98 machines, it has to
be able to emulate a true Shugart interface which means a /ton/ of
jumpers, not just one or two). Even today people in the CNC world try to
take PC98 machines to "computer repair" shops and get frustrated when the
IBM-PC compatible floppy drives they buy won't work in their PC98
computers.
1) My AT 1.2M drives (a sloppy, but not very
ambiguous name for it) can
also read and write 360K disks (a very sloppy but not very ambiguous
name for it).
BUT, not all can!
One of the very first "1.2M" drives that I got (an EARLY Mitsubishi
4854 with FIFTY pin interface connector!) could not reliably do "360K"
The speed was fixed at 360RPM (which is easily compensated for by a
300Kbits per second data transfer rate), and there was no provision for
alternate write current. LATER 4854 drives could do 360K just fine,
and switched to a 34 pin connector.
At the time, it made perfect sense, particularly in the world of
Japanese computing. NEC trotted out the PC98 model for PCs, which is
nothing like the IBM one. One of the more interesting aspects was that
the floppy format between 8", 5.25" and 3.5" disks is exactly the
same--8 xectors of 1024 bytes per track. There simply was no need for a
dual-speed 5.25" drive. I still have a couple of the Mitsubishis
stashed away. (The PC98 3.5" drives also spin at 360 RPM). Very
logical.
I seem to recall that NEC had a sort of sub-contractor for US support
and information down in the San Diego area. I may still have some of
their literature. I believe there was also an article or two in Tech
Specialist (or one of its later aliases) about the big differences
between the PC and PC98 platforms.
But you certainly see the NEC PC98 formats all over the CNC
world--another place where CP/M 68K was popular.