Re[2]: 6502 info.

-----Original Message-----
From: Neil Bradley <nb@synthcom.com>
To: <vectorlist@synthcom.com>
Date: Thu, 15 Aug 2002 18:17:29 -0700 (PDT)
Subject: Re: VECTOR: 6502 info.

>
> > > so if you suspect that a game is using illegal opcodes then try to use the
> > > original brand of cpu.
> >
> > So which, if any, vector video (arcade) games used illegal instructions on
a 6502?
> > That's the million dollar question.
> > I've never had trouble with subs in arcade games, but I've never tried a
65C02 in
> > one either.
> >
> > Is there a list (yet)?
> >
> > Neil - A, AD or LL use any?
>
> Nope. They are all straight up 6502 instructions. I've looked at the code.
> My emulator core doesn't support 65C02 instructions, but it runs all the
> 6502 vector games.
>
> IIRC, The 65C02 wasn't released until the early 80s anyway, right? That
> would be post LL and Asteroids, and even AD depending upon the timing.
>
> -->Neil
>
>
I am not sure about arcade use of 6502 versions,
 back then when i did the ocasional repair the chips where so expensive that i
always used 1 that was pulled from something else.

that pretty much meant that the replacement was allways older than the game it
went into!

I DO KNOW that this was a big issue at one time with programmers using the old
APPLE2 systems.

using dodgy opcodes saved a lot of memory and clock-cycles back then, so it was
common practice to use them on apple and commodore computers.
it had the added bonus of protecting against hackers because the codes where
very hard to find data on back then.

i have a manual somewhere from a comodore64 hacker-debug cartridge that lists
all the opcodes!

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Received on Fri Aug 16 14:10:43 2002