Re: Hardware emulation of 6509 using 6502?

Den Thu, 26 Jul 2018 04:10:15 +0100 skrev smf <smf@null.net>:
> On 26/07/2018 02:18, Mia Magnusson wrote:
> > Oh. But that must be the kind of software no-one wants to run? ;)
> 
> Someone wants to run pet software?
> 
> > Well, a cbm2 has hardware that's similar enough that I assume most
> > productivity software for PET would work.
> 
> I'm not sure the basic & kernal is even compatible enough for that. 
> Should be simple to try some programs in vice.

Well, the idea is to use a patched kernal and basic from a PET in the
upper part of a 64k ram bank on a B, with the video ram visible at
$8000 just like on a standard PET, but otherwise no I/O visible, and
let the patched PET kernal interact with a short piece of software in
the small ram area in bank 15.

> > Emulating a VIC 20 would require something like an interrupt routine
> > copying a 22*23 screen onto the 40*25 screen and translate the VIC
> > registers, or just let basic programs without most pokes/peeks run
> > by just inserting a line feed at position 22.
> 
> Make the kernal output stop at line 22 and patch the basic PEEK/POKE 
> commands to remap the screen coordinates.

... and then someone moves chargen v.s. video ram around and the
emulation can't really know which pokes were supposed to go to a
pre buffered screen ram v.s. chargen.

> You'd stick vic in a higher bank so that you can start vic 20 basic 
> programs at the right place.
> 
> You could add a timer to catch screen writes by assembly programs,
> I'm not sure it's worth the hassle.
> 
> >> http://sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?t=468
> > Seems like a bad idea :)
> 
> Probably, isn't everything commodore 8 bit related a bad idea?

Well, they got some things right :)
 
> Porting the vic20 emulator to the p500 seems like a very bad idea.



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