[Coco] high density floppy controller mods

Mike Pepe 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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