8 Sep
2023
8 Sep
'23
3:48 p.m.
> It would still be handy to have a USB device that
operates as a "normal"
> fully functional FDC.
On Fri, 8 Sep 2023, Anders Nelson wrote:
I agree, and that generic USB FDC is already
available:
https://github.com/dhansel/ArduinoFDC
If I can simply select 5 1/4 floppy mode and it'll work with an 8" disk, I
guess I don't need anything else?
An 8" drive and a 5.25" 1.2M drive look the same to whatever they are
connected to, with a few trivial exceptions
8" is 50 pin; 5.25" is 34 pin.
The very first 1.2M 5.25 that I encountered (purchased at a swap) was a
pre-release/prototype? Mitsubishi 4854, and had a 50 pin connector!
I heard from some of the usual unreliable sources that when the AT BIOS
was being modified for 1.2M, some of the programmers thought that IBM was
adding an 8" drive!
8" is 77 track, 1.2M is 80 track. Therefore, trying to format an 8" disk
as 1.2M without special software will fail on tracks 77-79
For writing, TG43 provides write pre-compensation. not needed for
reading.
BTW, 8" power connectors were not standardized, so different brands of
drives will need different connectors.
READY/DISK-CHANGED on pin 34 was not standardized, and can confuse the
system is wrong.
Ideally, you would also want 8" SSSD, as that was "THE STANDARD" format
for CP/M.
The PC formats are/were all 512 bytes per sector; other formats had 1024,
256, and occasionally 128.
Many PC FDCs can not handle FM/SD, and many can't handle 128 bytes per
sector.
I;m forgetting numerous other items, so those are left as an exercise for
the reader :-)
--
Grumpy Ol' Fred cisin(a)xenosoft.com