Re: Difference between 6502 & 65C02

[johnlb@primenet.com (John Bowling)]

In article <ralphp-2603960820040001@shr32-1.prysm.net>,
Ralph Wade Phillips <ralphp@prysm.net> wrote:
>Hi, David!
>
>In article <4j5ohj$p2s@atlantis.atlantis.actrix.gen.nz>,
>dempson@atlantis.actrix.gen.nz (David Empson) wrote:
>
>> In article <4ivuv4$rlc@crl11.crl.com>, Chet Gerhardt <aplworks@crl.com> wrote:
>> > 
>> > OK, How about a 6503 (I got one in a Platinum IIe a while back)?  A 
>> > Friend and I were chatting about this, what is the difference between a 
>> > 6503, a 65c02 and a 6502? :)
>> 
>> A "6503" _is_ a 65C02.  It is just Apple's part number (they were not
>> able to put a letter in the middle of the number, so they called it a
>> 6503, implying it is one better than a 6502).  It is probably an NCR
>> or GTE-sourced 65C02.  It definitely won't be a Rockwell R65C02, which
>> has several extra bit-manipulation instructions.
>> -- 
>> David Empson
>> dempson@actrix.gen.nz
>> Snail mail: P.O. Box 27-103, Wellington, New Zealand
>
>        Well, yes, it can be.  I worked at an Apple dealer during the
>start of the enhancement series (actually worked from 1981 to 1989 ... )
>and whereas the MAJORITY of the upgrades came with NCRs, several with
>GTEs, there WERE quite a few with the Rockwell 65SC02's.
>

Then, apparently, the difference in Rockwell's chip is not significant to 
standard programs on the //e.  Where the problems would come in would be 
with software that used an operation that was different on the chips, 
including those undocumented operations.

I can see Apple's desire to use chips from any manufacturer (best price),
but what would have happened if a small software manufacturer noticed that 
their //e had the Rockwell chip and assumed they all did?  No, they 
shouldn't do that, but they did use lots of undocumented opcodes and 
undocumented entry points in ROM in the early days, which are even more of a 
NO-NO.  What they did is the primary reason why there are programs out 
there that will not run on a //e or a gs.  And several of those companies 
were well respected at that time.

--
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John Bowling             |Apple II GS can whip the pants off its little
johnlb@primenet.com      |brother (Mac) any time!
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