12 Oct
2007
12 Oct
'07
11:01 a.m.
On 12 Oct 2007 at 13:41, M H Stein wrote:
No complaint about the idea of minimal first sector.
The specific problem that I was referring to is the incompatability with
trying to read Cromemco diskettes using an NEC 765 type controller, which
needs a larger index gap, resulting problems reading the first sector
of each track.
At the expense of crossing over into Tony's territory, it was easier
to make a simple WD1770 circuit on a Peecee ISA prototype board. The
software to interface to it is almost trivial.
I recently shipped a batch of formatted Cromemco DSSD 5.25" diskettes
to Germany made using this board. Customer reports that they worked
just fine.
I rather like the NEC 9801 approach--change the physical format, but
keep the data format the same. There's no logical difference between
the 9801 8", 5.25" and 3.5" diskettes--all are 77x2x8x1024 format,
360 RPM.
The first time I ran into the "first track is always FM" disks was on
ISIS-II on the MDS. Of course, that didn't help you if you had an FM-
only controller and were trying to boot an MFM floppy...
Cheers,
Chuck