By the way here is the skeleton code to determine if the processor is NMOS
or CMOS:
lda #$99
clc
sed
adc #$01
beq cmos
;if here it is nmos
nmos: ;put in code to say "NMOS" and exit
;if here it is cmos
cmos: put in code to say "CMOS" and exit
Rich Leary
On Friday, August 15, 2014 1:14:48 PM UTC-6, Rich Leary wrote:
>
> I purchased some 65C02's on eBay in June to use on my V1 6502 CPU board.
> While my wire-wrap CPU board used a 'C02' (GTE 65SC102-2 to be a little
> more definitive) I had never written any code that used the 'C02' added
> opcodes, addressing modes, or other features. My DOS/65 code uses strictly
> NMOS 6502 opcodes etc.
>
> I wrote a short utility that used BRA instead of JMPs and in one spot used
> an INC A opcode. The utility would not work leading me to question whether
> I had the residual brain cells to have fun with computers. I changed the
> code to remove any 'C02' opcodes etc. and the utility worked fine. I was
> now suspicious.
>
> I then used the few lines of code that perform BCD arithmetic as the NMOS
> 6502s do not correctly handle the flags when doing BCD arithmetic. The CMOS
> versions do correctly set the flags. This test clearly indicated that what
> was labeled a 65C02 (specifics in a minute) was not a 65C02 but was an NMOS
> 6502.
>
> Bottom line - the ICs appear to be intentionally mislabeled. So if you see
> an eBay add for a 65C02 with the following lines and with the Rockwell logo
> to the right of the first three lines be careful.
>
> R65C02P4
> 11450-13
> MEXICO
> 0815 S11468-4
>
> I did a quick eBay check and more than seller in China had IC pictures
> with this marking. Some may be correct but I suspect many are not.
>
> By the way, when I pulled the new 6502 V1 board and put my 30+ year old
> wire wrap board in my system to run the same tests on the GTE IC, it
> refused to start. I guess I really do need the V1 6502 CPU!
>
> Rich Leary
>
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