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 ....
The Z80 situation was much better
Also the 65C02 (the special CMOS version)
als was more reliable in this respect
Sipke de Wal
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http://xgistor.ath.cx
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----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <cctalk(a)classiccmp.org>
Sent: Friday, June 07, 2002 8:03 PM
Subject: Re: [CCTECH] Interesting tidbit on 6502
<snip>
Many processors (and other chips for
that matter) have undocumented
instructions used for factory testing.
-tony