Re: Apple IIe + ProDOS = Headache

[pausch@saaf.se (Paul Schlyter)]

In article <1gg1isg.1a35pyatdcuq8N%dempson@actrix.gen.nz>,
David Empson <dempson@actrix.gen.nz> wrote:
> Paul Schlyter <pausch@saaf.se> wrote:
> 
>> In article <20040625200651094+1200@News.Individual.NET>,
>> Roger Johnstone  <rojaws@orcon.net.nz> wrote:
>>  
>>> ProDOS technical note #23 says:
>>> 
>>>   ProDOS 8 1.3
>>> 
>>>   Warning: This is not a stable version of ProDOS due to an
>>>   illegal 65C02 instruction which was added. This version can
>>>   damage disks if used with a 6502 processor.
>>> 
>>> http://web.pdx.edu/~heiss/technotes/pdos/tn.pdos.23.html
>>> 
>>> I take it to mean that it was a valid 65C02 but invalid 6502 instruction,
>>  
>> The text said "illegal 65C02 instruction".  And since the 65C02 was
>> backwards compatible with the 6502 at the machine code level, it was
>> definitely an illegal 6502 operation as well.
> 
> The technical note was badly worded.  They didn't use an "illegal 65C02
> instruction".  It should have said that they "illegally used a 65C02
> instruction".
 
Even that is bad wording: there's nothing "illegal" in using opcodes in
a new processor which was unavailable in older processors.  After all
these new opcodes are there to be used, right?
 
A better wording would be: "used a 65C02 instruction not backwards
compatible with the 6502".  Yes, this phrase is a bit longer, but it
does tell well what actually happened.
 
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