[Coco] 80 track disk access under RSDOS

Bob theother_bob at yahoo.com
Wed May 5 23:06:35 EDT 2004

--- John Kowalski <sock at axess.com> wrote:
> At 01:16 AM 05/05/2004 -0700, Bob wrote:
> >Thanks for the info John. I'm still doing what I consider
> >"ongoing testing" and seem to have some issues reading
> >from 35 track disks when in 80 track mode, or maybe I have
> >a typo in my patch program.
> >
> What kind of issues are you having?

Well, attempting to use COPY is not working, so I think that
part of the patch may have a bug. I need to find the magazine
article and compare the program. If that's all correct, I'll
start looking at the Unravelled disassemly and see if I can
figure out the deal.

AFAIK the patch program patches all BASIC routines... 

I just realized... when using 80 tracks, you either have to tell
it to relocate the GAT table or only have open files on one drive
at a time (due to size limitation). If COPY is keeping the source
open while writing to the destination, the GAT table in memory is
probably getting corrupted. So a single drive copy might work in
that case, which I can verify because the 3P only has one drive.

It was only when I hooked up the external 2 drive bay to copy some
programs off of 5.25 disks that I started having problems with COPY.
> By the way, if you wanted to store a lot of 35-track-readable files onto an
> 80 track disk, you could write a simple program to mark 'used' all granules
> above 68 in the GAT (track 17, sector 2 - each byte represents a granule.)
> Then save up to 68 granules of files onto the disk.
> Then run another program to mark 'free' all granules above 68 in the GAT.
> Now you can keep adding more files to the 80 track disk, while all of the
> previously added files are guaranteed to load on a 35 track system.

Good idea (bearing Art's later comment in mind too!)
Sounds like a good (not great) way to copy protect a disk too.
Have a program enable 80 tracks after it starts, then restore 35
track mode before it exits. Intersting idea, but probably not so
useful today.

For me, I just need the first one granule program to load and it
enables 80 tracks (and other patches, like 6ms step, etc...)


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