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From: daveh@cbmvax.cbm.UUCP (Dave Haynie)
Newsgroups: net.micro.cbm
Subject: Re: unused 6502 instructions
Message-ID: <52@cbmvax.cbmvax.cbm.UUCP>
Date: Tue, 8-Apr-86 18:20:49 EST
Article-I.D.: cbmvax.52
Posted: Tue Apr  8 18:20:49 1986
Date-Received: Thu, 10-Apr-86 07:20:31 EST
References: <1037@h-sc1.UUCP> <608@nicmad.UUCP>
Reply-To: daveh@cbmvax.UUCP (Dave Haynie)
Distribution: net
Organization: Commodore Technology, West Chester, PA
Lines: 20

In article <1037@h-sc1.UUCP> mccauley@h-sc1.UUCP (john mccauley) writes:
>Does anyone have descriptions of what the reserved
>6502 instructions do?

Its incredibly foolish to use the "undocumented op-codes" in the 6502/6510
8502, etc.  While current NMOS processors like these all give similar
results, ALL of the CMOS processors, like the 65C02, 65C102, etc. either
completely ignore these unused op-codes (best case), or use them for the
REAL extended operations that the CMOS series have.  In either case, you
can't count on them working with a CMOS processor.  They have a similar
effect on the 65816 family of 16 bit processors that everyone seems to 
like talking about these days.  ALSO, most of these "instructions" can have
indeterminant side effects; a few can even lock up the processor to the
point where you'll have to power down to reset it.  There's very little
chance of any working in any future machines, please, don't use them,
you'll save yourself much more trouble than you think.
-- 

Dave Haynie    {inhp4,allegra,seismo}!cbmvax!daveh
               "When the going gets tough, the weird turn pro"