Re: Apple /// processor

[dempson@swell.actrix.gen.nz (David Empson)]

In article <1994Feb13.102857.2813@pro-vanilla.oau.org> davidh@pro-vanilla.oau.org (David Huggins) writes:
> Is there any advantage or problem with using a 65C02, rather that 6502
> in an Apple /// ? I've seen reference to ///'s running on the 65C02, but
> have no idea whether it's faster.

It wouldn't be any faster.  The 65C02's instructions require exactly
the same number of clock cycles as the 6502, and the clock speed is
set by the motherboard.  (A few instructions take one more cycle on
the 65C02, such as JMP indirect, and decimal mode arithmetic.)

The main advantages of the 'C02 are the new instructions and the fact
that it is CMOS, which reduces the power consumption.

I can't say whether or not a 65C02 would work in an Apple ///.  Some
models of the 65C02 don't work properly in the Apple ][+, possibly due
to bus timing or loading requirements.  The 'C02 works fine in the IIe
and IIc (obviously).

I suspect that it won't work very well - the Apple /// have special
hardware to extend certain addressing modes to support more than 64k,
and this hardware is unlikely to work with new 65C02 instructions.
Does the /// redefine (or add) any opcodes to the standard 6502 set?
If so, the 65C02 is unlikely to work.
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand