[Coco] 80 track disk access under RSDOS

Arthur Flexser flexser at fiu.edu
Wed May 5 12:22:31 EDT 2004

On Wed, 5 May 2004, (John Kowalski) wrote:

> 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.
>                                          John Kowalski (Sock Master)
>                                          http://www.axess.com/twilight/sock/

You'd also have to knock out the Disk Basic routine that zeroes out the
GAT above 68 grans.  This routine was defective in at least Disk Basic
1.0, if I recall, filling those grans above 68 with garbage instead of


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