Floppy disk: one drive per face
cisin at xenosoft.com
Thu Nov 5 15:50:14 CST 2020
On Thu, 5 Nov 2020, Enrico email.it via cctalk wrote:
> We are trying to read some floppy disk used on a 1981 Italian Z80 machine
> with CP / M.
> The problem is that the firmware selects face A of the floppy as DRIVE A and
> face B of the same floppy as Drive B.
> We saved an image with IMD and we know that the geometry of face A is IBM
> 3740 26x128x77 tracks.
> By inserting this data into the 22DISK definition file we can successfully
> extract the CP / M files from A side.
> How should we configure 22disk to be able to do the same thing on the B side
> of the same floppy disk?
> Inserting Side 2 in the definition table is not enough ....
An irrelevant data point, . . .
when double sided floppy drives came out for the PC/5150, there were some
patches informally distributed (ISTR mimeograpahed), for doing that with
PC-DOS 1.00! But, very soon thereafter, PC-DOS 1.10/MS-DOS 1.25 came out
that supported a full double sided format.
Is this an 8" disk? SSSD? (128 x 26 x 77)
(As you are presumably already aware, many PC FDCs have problems with FM
and/or 128 bytes per sector)
A really stupid HARDWARE way to do it would be to swap the wires for the
heads on the drive! Many drives have convenient plugs that would make
Another stupid hardware way to do it would be to jumper side select, to
falsely select second side.
Chuck has provided a straight-forward solution. There were several
different ways that disk formats were expanded to double sided.
Some went up side A, and then DOWN side B
Some made use of the faster head switching than track stepping, and did a
track on one side, then a track on the other side. (which is the "modern"
standard, for MS-DOS, etc.)
SOME went up side A, and then went back to track 0 and then up side B.
With one of those formats, you could simply tell it that the "reserved
tracks" occupied the entire first side. (77 reserved tracks from your
XenoCopy does not have such a format supported. I am not going to be
adding it at this time.
Uniform does not support it.
22Disk apparently has easily modified parameter tables, so should work
just fine. Thank Chuck!
Grumpy Ol' Fred cisin at xenosoft.com
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