Re: ROM Question

[david@uow.edu.au (David Wilson)]

dempson@actrix.gen.nz (David Empson) writes:
>As for the 6502: since the Apple 1 came out early in the life cycle of
>the 6502 processor, it is quite possible that it _wasn't_ the same as
>the version of the chip used in the Apple ][, ][+ and //e.  A few
>instructions were added to the 6502 after its original release, but I'd
>have to do some hunting to find the details.

The original 6502 (and I suspect the 6501 - the 6800 pin compatible version)
were missing the ROR instruction. I have never seen a 6502 old enough to
be missing this but my OSI Superboard has an 8KB Microsoft BASIC which
avoids the ROR instruction so I suspect that code dates from the original
chip [I have not checked to see if Applesoft has the same work around]. 
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia