Re: R65C02 PI

[nathan@visi.com (Nathan Mates)]

In article <4vgvr3$na8@nnrp1.news.primenet.com>,
John Bowling <johnlb@primenet.com> wrote:
>In article <4vd6qq$8qt@newsbf02.news.aol.com>, W12Ste <w12ste@aol.com> wrote:
>>In my IIe I found a 'R65C02 PI' with '65402-3' on the bottom is it a
>>standard 6502???

>It's a Rockwell 65C02.  It will work as a standard 6502, but may *not*
>properly replace the 65C02 in an Apple IIc or IIe.  Most software should
>work, but some code that is expecting the WDC 65C02 enhancements may break
>on the enhancements that Rockwell put into their version.

   Bzzzt! Referring to Lichty & Eyes book on the 6502, 65C02, 65802
and 65816, p. 561, shows that the Rockwell 65C02 is a _superset_ of
the regular 65C02. In other words, it's a WDC 65C02 _plus_ a few (32)
more instructions of their own.

   Where the incompatability shows up is that the opcodes used by
those 32 extra instructions are 1) treated as NOPs by regular 65C02s,
and 2) Have wildly different meanings on the 65802/65816. Thus, code
using the extra features of the R65C02 won't run correctly on anything
but a R65C02.

   In case I haven't quoted enough from Lickty & Eyes's book the past
week, I'd really encourage anyone who wants to comment on the guts of
the 6502, 65C02, R65C02, 65802 and 65816 chips to pick up a
copy. There was a rumor that WDC was selling [photo]copies a while
back; anyone care to confirm or deny it?

Nathan Mates

--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
# What are the facts? Again and again and again-- what are the _facts_?
# Shun wishful thinking, avoid opinion, care not what the neighbors
# think-- what are the facts, and to how many decimal places?  -R.A. Heinlein