I nearly did.
It was just that I couldn't find a spare 3.5" drive when I
had the M4 in bits. One day I'll come across one. I don't use 3.5" disks
much, apart from on the PCs. The other machines have 'real' disk drives :-)
I am also a great believer in making measurements rather than just trying
it (which seems, alas, to be the modern thing to do). What if it works. I
don't know if the pulse rate really is similar, or if I was just lucky
and the drive could handle a strange data rate. By making the
measurement, I know what is going on.
My understanding back when the 720K 3.5 was being develeoped was that it
was INTENDED to be fully interchangeable with the 5.25". Therefore, it
"should" be OK, if the design spec for full interchange was adhered to..
BUT, there's always the possibility that "because NOBODY EVER uses FM
anymore,..." that they could have cut some corners that might interfere
with something that is still nominally part of the spec. That, of course,
could differ from one brand of drive to another.
I believe the 3.5" drive will work as well.
That's what this discussion
is about. If it doesn't, I will have to investigate why not, since all
the measurements I've made so far say that it will.
there are the INTERESTING ones:
Most PC controllers keep the drive turning at
360rpm and use the 300kbps
MOST. I was surprised the first time that I encountered the dual
1.2 XT: To handle 1.2M diskettes in PC/XT, which only supported a
250K data transfer rate, Weltec made a 1.2M drive that ran at 150 RPM!
Surely it should be 180rpm (== half the 360rpm of a normal 1.2M
disk with the 500kbps data rate).
That's right. 180RPM. Sorry.
That's one I've never seen....
don't think that it was around for long.
Tandon TM100-4M: 100TPI, instead of 96. I think that the M may have
stood for "Micropolis", who were the early 100TPI.
3": common in some circles
3.25": Dysan bet the company on soft-sided floppies. Has anyone ever
seen one in anything other than a Seequa Chameleon 325? Anyone ever seen
the 325? Anyone need some used blank floppies? I might even still have
an alignment disk or 2.
67.5TPI (40 track) 3.5": used for the Epson Geneva PX-8
Anyone know what the RS M100 "Portable disk drive" FIRST model used? Was
2.8 M Barrium Ferrite:
Amlyn: weirdest drive that I've got. Somewhat deeper than usual full
height 5.25, sticking out quite a bit. Used a holder holding 5 600
Oerstedt diskettes, with disk changing under software control, for a total
of 6M. Was marketed for PC/XT, so it had it's own controller. Supposedly
used analog positioning, and could handle 48, 96 and 100 TPI! I'll
believe that if/when I can finally get around to checking it out.
Or how about whatever fit the Canon CMD 500 SS drive that used a floppy
approximately 4" wide? I have two of the drives, no disks, and no idea
as to what they were used in!
Fred Cisin cisin(a)xenosoft.com
Don Maslin - Keeper of the Dina-SIG CP/M System Disk Archives
Chairman, Dina-SIG of the San Diego Computer Society
Clinging tenaciously to the trailing edge of technology.
Sysop - Elephant's Graveyard (CP/M) Z-Node 9 - 858-454-8412
see old system support at