[net.micro.cbm] unused 6502 instructions

mccauley@h-sc1.UUCP (john mccauley) (04/07/86)

Does anyone have descriptions of what the reserved
6502 instructions do?

	Thanks,

	Scott McCauley
	mccauley%h-sc4@harvard.HARVARD.EDU
	....!harvard!h-sc4!mccauley.UUCP

brown@nicmad.UUCP (04/08/86)

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

In the October issue of "COMPUTE!" magazine, there is an article on the
hidden world of the 6502 'Hidden Instructions'.

If you can't find a copy of said article, drop me an email message and
I will tell you about them.
-- 

              ihnp4------\
            harvard-\     \
Mr. Video      seismo!uwvax!nicmad!brown
              topaz-/     /
             decvax------/

daveh@cbmvax.cbm.UUCP (Dave Haynie) (04/09/86)

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"