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From: 50723995@ucs.uwplatt.edu (Bill Zwicky)
Newsgroups: comp.sys.cbm
Subject: Re: Undocumented 6502/6510/8502 instructions?
Message-ID: <1990Nov18.000434.211@ucs.uwplatt.edu>
Date: 18 Nov 90 06:04:33 GMT
References: <4125.27440883@cc.nu.oz.au> <1990Nov16.214729.27679@Neon.Stanford.EDU>  <1990Nov17.211343.17356@funet.fi>
Lines: 29

In article <1990Nov17.211343.17356@funet.fi>, po87553@korppi.tut.fi (Pasi 'Albert' Ojala) writes:
> In article <1990Nov17.185259.10564@evax.arl.utexas.edu> cs4344af@evax.arl.utexas.edu (Fuzzy Fox) writes:
>>The reason that many games crashed on the
>>128 is that they would often accidentally twiddle some memory locations
>>that differ between the 64 and 128 (such as $D030, which does nothing on
>>the C64 and can switch to 2 MHz-no-video mode on the C128).
>>..
> 
> I will surely disagree. The real reason for crashing was the fact that
> undocumented commands did't work on 8502 at all. At least all these so
> called undocumented op-codes were 'accidents' produced by the other
> commands and the processor design. I am sure that both 6502 and 8502
> differ significantly in their inner design.
> 
> Pasi Ojala, Sysop Of Pasbox

There has never been a need for serious design changes between the 6502,
6510, and 8502; the 6510 is a 6502 with a built-in parallel port, and the
8502 is a 6510 that can run a 2 MHz.  (Trust me; if a co. doesn't need to
make changes, they won't)  I've run numerous games on my 128, and I know
several of them use undocumented opcodes, but still run fine. The only
progams that have failed to work are ones that jump into 2 MHz mode, then
try to do something that can't cope with the speed (ie. try to access the
serial bus).


|)         /    Bill Zwicky                   /    |/
|)itman    /    50723995 @ UWPlatt            /    o  Left-handed widget
           /    50723995 @ UCS.UWPlatt.EDU    /   '