Re: Difference between R65C02 and original 6502 (wrt 6509 emulation)

Mia Magnusson wrote:

> Something that Michal and you might want conteplate: Would there be any
> benefit for the new 8088 support software if it were possible to hide
> the $0/$1 registers in '816 native mode?

I am wondering about this. That would necessarily mean that the IPC
library would run in '816 mode, which would mean that there could be no
KERNAL calls unless the KERNAL is rewritten for the '816?

> (For example, when emulating an MDA display adapter, the first 
> char and its corresponding attribute can
> afaik not be read by the 65xx processor so any transfer from the
> emulated MDA display to the CBM-II native display would need at least
> two bytes copied to some other location by the 8088 processor. 

Yes, this is how it's currently done.

> Also disk operations that read/write memory feely can't access the first
> two bytes in every 64k block. Maybe the benefit of being able to hide
> those two registers is less than the cost (in work and chip usage) to
> actually implement this though. Sorry if I'm bringing up stuff that
> we've already discussed.

But disk reads call the KERNAL IEEE routines extensively, so it would be
very nontrivial to use them in '816 mode?

Regards,
Michau.