[Coco] Disk Basic and 512 byte block floppies.

[Robert Gault]

tim lindner wrote:

> John E. Malmberg <wb8tyw at qsl.net> wrote:
> 
<snip>
>>I formatted a 720K 3.5 inch floppy with 512 byte sectors
><snip>
> 
> Interesting experiement.
> 
> The size of each sector is written to the disk. Disk BASIC expects all
> the sectors to be 256 bytes, it doesn't check. It create 256 byte blocks
> of RAM to read to and from these sectors.
> 
> If the sector is larger, then the RAM buffer will overflow. On a read
> sector command you will overwrite whatever is past the sector buffer in
> RAM. The could be dangerous.
> 
> On a write sector command you will write whatever data is after the
> buffer to the larger sector.
> 

With Disk Basic, the buffer overflow will go into a second disk I/O 
buffer; buffer0 $600-$6FF, buffer1 $700-$7FF. You would corrupt data 
stored in the second buffer but in most cases you won't see any ill effects.

In general, 512 byte/sec floppies can be used in this fashion on a Coco. 
Just don't expect these disks to then make any sense on a PC.