Processors sometimes spelled with C

[jeffythedragonslayer]

I notice that these processors are sometimes spelled with "C" and sometimes not, like 65C02. Why is that; does the "C" mean Commodore? Is it more official when spelled with a "C?"

[commodorejohn]

CMOS, generally. The 65C02 specifically is a partial redesign that adds some new instructions and tidies up a few issues compared to the original NMOS 6502.

[Dr Jefyll]

commodorejohn wrote:

CMOS, generally.

Yes.

Quote:

a partial redesign that adds some new instructions and tidies up a few issues

True, but as you probably know, that's incidental.

As compared to the older NMOS process, CMOS is a chip fabrication technology noted for attributes including better noise immunity and much lower power consumption.

It would've been possible and beneficial to simply migrate the old 6502 directly to CMOS. But it happens to be a good opportunity for making improvements, given that a redesign will be required in any case.

-- Jeff

[GARTHWILSON]

To compare CMOS logic (used in the 65c02) to NMOS logic (used in the original 6502), see:
https://en.wikipedia.org/wiki/CMOS
https://en.wikipedia.org/wiki/NMOS_logic

Quote:

The 65C02 specifically is a partial redesign that adds some new instructions and tidies up a few issues compared to the original NMOS 6502.

Yes; the 65c02 did not just implement the same 6502 design in a different process, but made many significant improvements. See http://wilsonminesco.com/NMOS-CMOSdif/ .