[Coco] HDB-DOS at 16K

[Arthur Flexser]

On Tue, 16 Mar 2004, Boisy G. Pitre wrote:

> Hi Art,
> 
> I'm thinking of adding some features to HDB-DOS, but in doing so, would 
> have to use the extra 8K ROM area at $E000-$FDFF.  I'm curious what 
> kind of incompatibilities would something like this bring to a CoCo?  
> Aside from the obvious need for a disk controller to support a 16K ROM 
> size, did you find that Extended ADOS-3 suffered major compatibility 
> with certain programs?
> 
> Also, are there any special considerations that one has to take into 
> account with the way the CoCo 3 ROM code moves ROM into RAM?
> 

The only really really bad compatibility headache that I can recollect
offhand was with a program that put its stack above $8000, which went away
when I switched into ROM mode (Word Power 3).  I think Telewriter 128 also
had a problem due to turning off the "constant RAM at $FE00" bit that
caused a critical vector to disappear when ROM was switched in, but I was
able to solve this by putting copies of the vectors into the ROM at
addresses matching the RAM ones.

Art