Re: Enhanced //e with a 6503??!

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

<heuser.marcus@freenet.de> wrote:

> > I recently scored an enhanced //e (verified that it can display
> > mousetext and DHGR) -- however, it was sent to me with a processor
> > manufactured in mexico, labeled as a 6503.
> 
> I guess that you have a "Rockwell 338-6503". This would be the same
> chip I have in one of my boards ("International NTSC"-type from 1986,
> salvaged from an enhanced French //e).

This agrees with what I've heard: some companies made a "6503" which was
another name for the "65C02", not to be confused with the earlier "6503"
which was a smaller package version of the "6502" which only had 28 pins
and a much smaller address bus.

> In one usenet post I read that this is simply another name for the
> 65C02 made by Rockwell but I don't know if this is correct as there is
> another, not totally 65C02-compatible chip: The 65SC02 from GTE, which
> does not have the BBR, BBS, RMB, SMB instructions of the 65C02.

Hang on, you have it backwards.

The standard 65C02 was made by Western Design Center and second sourced
by companies like GTE. It does NOT contain the bit manipulation
instructions you mention.

Rockwell's version of the 65C02 (R65C02) adds the extra BBR, BBS, RMB
and SMB instructions (all of the x3, x7, xB and xF opcodes). In a
"normal" 65C02, these opcodes are all NOPs.

The same opcodes were reused on the 65802/65816 for completely different
functions, so if any code attempts to use these opcodes to take
advantage of the Rockwell R65C02 then it will probably crash on a IIgs,
unless it uses some special code to be certain it is running on a
R65C02.

Similarly, code which attempts to use 65802/65816 instructions has to be
very careful to check that is actually running on one of these
processors and not a 6502, 65C02 or R65C02.

"Programming the 65816 et. al." by Eyes & Lichty had a routine to
distinguish between a 65816/65802, 65C02 and 6502, but it didn't allow
for the R65C02. I managed to come up with an extension to this function
to also check for an R65C02.

A "Platinum IIe" I have here has a G65SC02 (presumably GTE), which will
be fully compatible with the standard WD65C02.

-- 
David Empson
dempson@actrix.gen.nz