HP 9816 CP/M-68K

[Eric Smith]

On Mon, Feb 12, 2018 at 1:23 PM, Fred Cisin via cctalk <
cctalk at classiccmp.org> wrote:

> Reading or writing multiple sized sectors can be done with multiple passes.
> But, I don't know how to FORMAT a track with multiple sector sizes with
> NEC 765 type controller.  Not as hard with WD style controllers.
> With multiple sector sizes, can squeeze 440K on a "360K" disk.
>

Format a track with the sector size that occurs later on the track, with
dummy sectors ahead of them and gap sizes selected to position them
properly.
Start formatting with the sector size for the earlier sectors. Abort the
format at the time when the desired number of sectors have been written.

I'm not sure whether there's any way to abort a track format on a PC. I did
it on a machine that had control over the μPD765 reset pin.

Definitely much easier with the WD style controllers.

It is possible to format disks on an NEC style controller with a format
that cannot be created on a WD style controller, for instance using
particular track or sector numbers above 0xf0, which are specially
interpreted by the WD during a track write.