[Coco] high density floppy controller mods
lamune at doki-doki.net
Fri Aug 4 18:47:43 EDT 2006
> The extra gaps required for the additional 18 sectors may make things
> pretty tight. Isn't that why PC disks went to 512 bytes per sector (to
> double the data bytes per-track without increasing the sector count)?
> In any event, to modify Disk Basic 1.1 (2.1) to format more
> sectors-per-track, you need to poke the new sector count into the
> following addresses:
> $D5B6 $D5B8 $D5C5 $D5C9 $D5D2 $D67B $D6BC
> Also note that the DSKINI routine will only check to make sure that
> there is enough unreserved memory available in the 32K Basic RAM to
> format the standard 18 sector track.
> If you want to allow the DSKI$ and DSKO$ commands to be able to read and
> write to the higher sector numbers, then you should poke the new sector
> count minus one into location $D540.
> DISCLAIMER: I have never actually tested this, so I can't gaurantee that
> these are the ONLY changes required. You should check out the Disk Basic
> Unravelled book to learn more about the ROM routines.
Well, guys, this thing really works.
Thanks to Warren's post and some poking, I wrote a little program that
writes data to 35 tracks, 36 sectors. Then it reads it back and compares
it, and I got 100% verification of the written data. 1224 sectors!
Very cool. Wish I had thought of this 10 years ago.
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