Re: Reading Commodore 900 disks in the 8250 (LP)

On Wed, Jan 10, 2024 at 2:26 PM <groepaz_at_gmx.net> wrote:
>

> You'll have to write custom drive code (obviously), but i don't see how it's
> not possible. (Some protections used "long sectors")
>

I agree, it should be possible to write/read any format provided that
you can figure out the
correct code and have enough RAM inside the 8250 to run it.
HOWEVER:

according to this page
https://www.zimmers.net/cbmpics/c900.html

The 900 has a 96 tpi floppy drive, the 8250 has (for sure) 100 tpi
drives. These two drives have tracks in
different positions and you won't be able to read/write disks
formatted by the 96 tpi drive on a 100 tpi drive.
The "good" news is that probably a regular IBM-PC HD drive can
read/write those disks if you can make the spindle go at 300 rpm
instead of 360 rpm (which is the default for HD drives) or you figure
out a clock ratio to encode/decode the format at the different speed
(greasewezle is probably your friend here).

HTH
Frank IZ8DWF