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Thread: The 6502 variants.. all the same?

  1. #1
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    Default The 6502 variants.. all the same?

    So I think I just found my 3rd bad 6502 Cpu (inside an apple III). Literally this is maybe the 3rd one I ever have seen fail [I think the other 2 that failed were in a commodore 1541 and and apple II plus]. They are just made really well it seems. At this point I have more 65C02 spares than regular 6502's lying around so i went on ebay to see what was available.

    When you first do a listing you get a plethora of R6502 cpu's. These are the Rockwell variants correct? Are they pin compatible with a standard 6502? The one that went bad was an SY6502.

    Mick

  2. #2

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    Best way to find out is to look for a pin out diagram Here is a link to it.

    https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAI


    It looks similar but there is always the possibility of error. I would check them compared to a regular 6502

  3. #3

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    It looks like the Rockwell 6502 can hit 2MHz, rather than the 1MHz of the original 6502s, much like the Synertek ones the Apple III used. The 1980s era 65C02s are directly compatible with MOS ones, at minimum. Some may be able to hit or exceed the 2MHz that the Apple III needs. Only the modern WDC ones should have slight incompatibilities versus 1970s-1990s era 6502s.

    (and yes the R6502 is made by Rockwell, and *should* be a perfect drop in replacement)

  4. #4
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    Thanks EPO, I am familiar with the mods that the modern WDC chips have but I thought that was just the 65C02, I didnt know they still make a vanilla 6502. I ended up buying a rockwell chip for around $7.00

  5. #5
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    Isn't there a recent variant that allows a single digit per second clock pulse? Something an original 6502 couldn't do.

  6. #6

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    The 65C02 has the illegal opcodes removed (breaks some software) and the WDC one has a different pin-out and needs an adapter.

    But apart from that, if it says "6502", it will work as a replacement.

  7. #7
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    Timo You Dont need to buy an adapter. They tell you how to modify two pins on their website by the way. Ive done it its pretty easy.

  8. #8

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    You may not *need* an adapter, but it makes things much cleaner-looking than bending and rewiring the legs.

  9. #9
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    Default

    But its inside the machine and no one sees it. And adapters cost money. Both options work and both are reversible. Either way its nice to have a 65c02 option. I was at a loss when one died in my IIe until I found WDC still makes a variant.

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