Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!evax!cs4344af
From: cs4344af@evax.arl.utexas.edu (Fuzzy Fox)
Newsgroups: comp.sys.cbm
Subject: Re: Undocumented 6502/6510/8502 instructions?
Message-ID: <1990Nov18.042630.17360@evax.arl.utexas.edu>
Date: 18 Nov 90 04:26:30 GMT
References: <1990Nov17.163800.12713@funet.fi> <1990Nov17.185259.10564@evax.arl.utexas.edu> <1990Nov17.211343.17356@funet.fi>
Organization: Computer Science Engineering Univ. of Texas at Arlington
Lines: 15

In article <1990Nov17.211343.17356@funet.fi> po87553@korppi.tut.fi (Pasi 'Albert' Ojala) writes:
>
>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.
>

The differences between the 6502 and 8502 are that the 8502 has an I/O
port at address $00/$01, and the 8502 can run at 2 MHz rather than just
1 MHz.  There was no need to redesign the way the processor works at
all, so all instructions are processed exactly the same way, right down
to the "bugs" in the hardware (ie, JMP ($xxFF) has the same incorrect
result on both processors).