Re: C64 MMU POC

On 7/8/2019 8:44 AM, Mia Magnusson wrote:
> A good thing about the C128 MMU is that it has two sets of registers.
> One full set that sits in the general I/O area, and a smaller set that
> sits in the $FFxx range (iirc). That way you can do a limited set of
> operations even when the full register set is invisible.
OK.  I will see if I can implement that.
>
> Are regular non-MMU-aware C64 programs supposed to be able to run even
> with the MMU active, or is it more intended for experimentation and
> MMU-aware software? This would greatly affect how important it is or
> isn't to be able to hide the MMU registers from unaware software.
As with all my efforts, if it turns into something more than just an 
experiment, I'd want it to be added to the 64 without adversely 
affecting any operation.  So, I'd work to "hide" the system from the 
memory map unless something knew how to enable it.
>
> I don't know of any C64 software that won't run on a C128. My
> conclusion is that it should be safe to map registers in the I/O areas
> that differs between a real C64 and a C128 in C64 mode.
Again, I try to make things compatible with both systems, so I'd prefer 
to stay away from spots where the C128 would have issues.
>

-- 
Jim Brain
brain_at_jbrain.com
www.jbrain.com