[Coco] Preliminary Support for SDC in HDBDOS

[Arthur Flexser]

On Tue, Nov 25, 2014 at 6:08 PM, William Astle <lost at l-w.ca> wrote:

> On 14-11-25 03:59 PM, Arthur Flexser wrote:
>
>> On Tue, Nov 25, 2014 at 5:19 PM, William Astle <lost at l-w.ca> wrote:
>>
>>
>>> 2. Interrupts. You need to make sure that any interrupt handling does not
>>> occur in the upper 8K of the "ROM" space since that will crash when the
>>> map
>>> is switched. Disabling interrupts would be overkill, though, since you
>>> can
>>> just make certain that no interrupt handling happens in the upper 8K.
>>>
>>>
>> Disabling interrupts when dropping into ROM mode would definitely not be
>> overkill if you want this modified ROM to be able to run software that
>> might be putting its interrupt handling anywhere at all.
>>
>
> Yes, that's a fair point. One would also want to make sure any DSKCON
> extensions located in the upper 8K could handle the data buffer being in
> "high" RAM, too, for the same reason.
>
> That said, how much such software is out there? That is, software that
> uses RAM above disk basic while still actually using the disk ROM? Of that
> software, how much of it actually modifies the interrupt handling with a
> routine in high RAM?
>
>
There's not a lot, but there's definitely some, and it's often frequently
used stuff like word processors.

The worst situation I ever ran into with Extended ADOS-3 compatibility was
a word processor (Word Power 3.x) that put its STACK in that upper 8K
area.  Never could come up with a compatibility fix for that one.  The
author promised to move the stack elsewhere in a later version, but never
did.

Art