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From: hsu@eneevax.UUCP (Dave Hsu)
Newsgroups: comp.sys.apple
Subject: Re: 6502-65C02
Message-ID: <861@eneevax.UUCP>
Date: Sun, 3-May-87 11:45:35 EDT
Article-I.D.: eneevax.861
Posted: Sun May  3 11:45:35 1987
Date-Received: Sun, 3-May-87 21:57:47 EDT
References: <8704281927.aa23754@SPARK.BRL.ARPA> <734@puff.WISC.EDU> <461@uhccux.UUCP>
Reply-To: hsu@eneevax.umd.edu.UUCP (Dave Hsu)
Organization: The Royal Maryland Wormucking Institute
Lines: 31

In article <461@uhccux.UUCP> yuan@uhccux.UUCP (Yuan Chang) writes:
>In article <734@puff.WISC.EDU> schumann@puff.WISC.EDU (Christopher Schumann) writes:
>>The latest discussion here says that the 65C02 doesn't work in older ][+'s
>>because they have a small(?) timing problem.
>>
>>Chris Schumann (6502 Guru)		schumann@puff.wisc.edu
>
>    I thought it'd be due to all those "undocumented" instructions that people
>use like crazy for copy-protection?  Unless all they did with the 65C02 was
>to document those opcodes...
>     Ever seen one of those programs that's made up of more than 5% of those
>"undocumented" opcodes?  Hard as h*ll tracing the thing.
>-- 
>- Yuan Chang -

Nawwww, you just need more practice.  The 65C02 did NOT document those
opcodes; they simply used them for other functions.  If I remember
correctly, GE pulled some one-upmanship and used some of the 65C02's
undocumented codes to implement some bit manipulation in THEIR 65C02.

Besides, the undocumented codes weren't as good as they were cracked up
to be for copy protection.  Safer to stick with simple stuff like
munging disk timings and the unsuccessful-page-crossing bug (which is
fixed in the C02, btw)

-dave "I don't remember any 6502 anymore" hsu
-- 
David Hsu			Nobody In Particular
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