Re: Difference between 6502 & 65C02

[johnlb@primenet.com (John Bowling)]

In article <4ivuv4$rlc@crl11.crl.com>, Chet Gerhardt <aplworks@crl.com> wrote:
>John Bowling (johnlb@primenet.com) wrote:
>: In article <96082.140914JCA31@maine.maine.edu>,  <JCA31@MAINE.MAINE.EDU> wrote:
>: >I'd like to know what it is that's different between these two cpu's,
>: >apart from one being a CMOS chip. I'm also curious as to why I my II+
>: >'sort-of' works with a 'C02 in it. I'd think that the machine would
>: >either run, or crash miserably, but instead, it just seems to have
>: >trouble keeping track of numbers ..?something to do with operating
>: >modes, maybe?
>: >
>: A 65C02 will work in place of a 6502 unless you are running code that has 
>: used 'undocumented' operations in the 6502.  Some of those undocumented 
>: operations were used as part of copy protection as well as trick code.
>: If the code is ALL standard 6502 code, you should not have a problem.
>
>: Several new op codes were put into the 65C02, which improve it's operation.
>
>: There is another possible problem:  Not all 65C02s are the same.  
>: Rockwell created their own 65C02 with a series of bit operators which are 
>: not part of any other manufacture's 65C02.
>: --
>: ------------------------------------------------------------------------------
>: John Bowling             |Apple II GS can whip the pants off its little
>: johnlb@primenet.com      |brother (Mac) any time!
>: ------------------------------------------------------------------------------
>
>OK, How about a 6503 (I got one in a Platinum IIe a while back)?  A 
>Friend and I were chatting about this, what is the difference between a 
>6503, a 65c02 and a 6502? :)
>
>Chet

I don't have any reference books on these anymore, but from what I recall 
there were a half dozen processors between 6501 and 6510, and the primary 
differences were the number of pins and how much memory they addressed.  
A few may have contained internal RAM/ROM.  It doesn't seem like a 6503 
would be software compatable with the IIe (designed years before the 
65C02, as were all 65xx processors [without the C]) so it was probably a 40 
pin 6502 with internal RAM/ROM.  Possibly used because Apple found a 
bunch of them surplus and wanted to save some money. 

It can't be 65C02 compatable unless it was designated a 65C03, and I 
don't recall ever hearing about such a chip.

John

--
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John Bowling             |Apple II GS can whip the pants off its little
johnlb@primenet.com      |brother (Mac) any time!
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