7 Jun
2002
7 Jun
'02
7:28 p.m.
see below, plz.
Dick
----- Original Message -----
From: "Sellam Ismail" <foo(a)siconic.com>
To: <cctalk(a)classiccmp.org>
Sent: Friday, June 07, 2002 1:03 PM
Subject: Re: [CCTECH] Interesting tidbit on 6502
There was considerable variation among the CMOS implementations of the 6502.
Some had the same, more or less, enhancements in the bit manipulation
instructions and read-modify-write instructions, and they all included the
wait-on-write cycles, which the NMOS versions lacked. AFAIK, only the
Rockwell CMOS version had the jump-indexed-indirect instruction, though.
On Fri, 7 Jun 2002, Sipke de Wal wrote:
Has anybody got examples, not including the CMOS versions, of course, which
are documented to be different, of differences in the NMOS 6502's? In the
years that I used 'em, I only had hands-on contact with MOS Technology,
Synertek, and Rockwell parts.
Problem with the 6502 is that different versions
from different manufacturers had different
undocumented instructions. So for the general
public this was not much of a boon ....
True.
The Z80 situation was much better
Also the 65C02 (the special CMOS version)
als was more reliable in this respect
The 65C02 actually has additional instructions which invalidate former
"undocumented" instructions on the 6502.
Sellam Ismail Vintage Computer
Festival
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