Re: WDC 65C02

[heuser.marcus@freenet.de]

> Can MOS 6502 be replaced with WDC65C02 Microprocessor?
> The WDC can fit with Atari 8bit family and Apple II family...

Apple II -> yes

Atari 8 bit -> no!  (at least not as a simple replacement)
The Ataris use a modified 6502 - called 6502B. It differs in only one
feature from the normal 6502: It has a special interrupt line which the
graphics processor ("ANTIC") uses to stop the 6502 and gain DMA access
to the RAM.
The 6502B is therefore not pin-compatible. You 'd have to build extra
circuitry to add this interrupt line to a "standard" CPU like the 6502
or 65C02. And if you have to do that you may use a powerful CPU like
the 65816. (Then a plethora of other problems will arise - like system
timing. But that's another story .)

C64 -> no! (I know you didn't ask ;-)
The C64 uses a 6510 which is a 6502 with two additional registers (at
addresses $0000 and $0001) to control the memory management (disabling
the system ROMs, for example).
So its even more complicated than with the Ataris - which didn't stop
people to build accelerators, though...

bye
Marcus