Re: 65c02 in an Apple II+?

[mjmahon@aol.com (Michael J. Mahon)]

Wayne Stewart wrote:

>Ernest wrote:
>> Can a 65c02 processor be used in a II+? I have a brief article from a Basis
>> 108 SIG newsletter that states:
>> 
>> "Bill then remarked that he recently installed a 65c02 processor in his
>> Basis 108 and it runs flawlessly. He recommends the GTE chip as being the
>> best of all available chips. Rockwell has implimented serveral additional
>> commands but has so altered the timing chain so that their chip requires
>> substantial board modifications to be used."
>> 
>> Has anyone tried installing a 65c02 chip in an Apple II+. The Basis is II+
>> compatible and I am considering the swap, and I have a GTE chip that I can
>> use. Is there any  reason why I should not try this -ie, in the words of a
>> famous NASCAR driver, will I "hear something smoking" if I try this?
>
>I've successfully used two different 65C02s in the II+. The GTE and the
>Rockwell. I tried other brands of 65c02 but had no luck. The main reason
>I wanted a 65C02 was so I could use the latest version od ProDOS on the
>II+ hard drive.

In _Understanding the Apple //e_, Jim Sather writes that the NCR 65C02s
that he tried did not work, even though they were 2MHz chips.  He makes
an educated guess that the problem is that data read from the main memory
on the ][ and ][+ arrives at the 65C02 with insufficient setup time (only about
50ns--technically within spec, but clearly marginal in the chips he tried).

The 6502 is much more forgiving, as are the Rockwell 65C02s.

Interestingly, he puts the GTE chips in the same category as the NCRs.
BTW, the data from the 16KB card arrives in plenty of time for all 65C02s.

-michael

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