[Coco] 40 track HDB-Dos

[Robert Gault]

Chad H wrote:
> You mean accessing the  disk as a single double-sided 'drive'?  Haven't seen
> HDB-DOS do that yet.  I think there is a POKE you can call to set the drive
> to 40-tracks though I don't recall the specifics right off hand.  I just use
> Drive's 0/2 for both sides of one drive, and Drive's 1/3 for both sides of
> the other.
>

HDBDOS and the RGBDOS for emulators can't treat drives under Basic as single 
double sided drives. You can easily read both sides of a double sided drive as 
individual single sides by changing the drive table at $D89D which defaults to 
1,2,4,$40. Change it to 1,2,$41,$42 and drives 2 and 3 become the second sides 
of drives 0 and 1 respectively.
While it is easy to access sectors of a 40 or 80 track drive by changing some 
bytes in the DOS, there is no way to HDBDOS can handle a directory for an 80T drive.
Try poking bytes $D29D (40),$D534 (39), $D65F (40), and $D682 (40) to change 
HDBDOS to a 40T system. No guarantees and study "Disk Basic Unravelled" DOS1.1 
to see what these bytes control.