see below, plz.
Dick
----- Original Message -----
From: "Sellam Ismail" <foo_at_siconic.com>
To: <cctalk_at_classiccmp.org>
Sent: Friday, June 07, 2002 1:03 PM
Subject: Re: [CCTECH] Interesting tidbit on 6502
> On Fri, 7 Jun 2002, Sipke de Wal wrote:
>
> > 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.
>
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.
>
> > 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.
>
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.
>
> Sellam Ismail Vintage Computer
Festival
> ----------------------------------------------------------------------------
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>
Received on Fri Jun 07 2002 - 19:28:27 BST