Author Topic: Z80 CPU NMOS or CMOS  (Read 5261 times)

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Offline arnoldemu

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Z80 CPU NMOS or CMOS
« on: 15:43, 06 January 16 »
I believe almost all CPCs use NMOS cpus.

NMOS:

OUT (C),0
LD A,R/LD A,I -> P/V flag is cleared if interrupt is received during the execution of these commands.

CMOS:

OUT (C),0 actually does OUT (C),255
LD A,R/LD A,I -> no bug

I tested the Z80 in my GX4000 and CPCs and all are NMOS. Are there any CPCs with CMOS Z80's?

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Offline gerald

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Re: Z80 CPU NMOS or CMOS
« Reply #1 on: 16:03, 06 January 16 »
I believe almost all CPCs use NMOS cpus.

NMOS:

OUT (C),0
LD A,R/LD A,I -> P/V flag is cleared if interrupt is received during the execution of these commands.

CMOS:

OUT (C),0 actually does OUT (C),255
LD A,R/LD A,I -> no bug

I tested the Z80 in my GX4000 and CPCs and all are NMOS. Are there any CPCs with CMOS Z80's?
I do not think Amstrad ever used a CMOS Z80.
Even on the later Plus/GX4000, it's a NMOS Z8400 (CMOS would be Z84C00)
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Re: Z80 CPU NMOS or CMOS
« Reply #2 on: 18:40, 06 January 16 »
Using a CMOS Z80 into a CPC will cause some programs failure.
For example, STarKos will not work!
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Offline TFM

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Re: Z80 CPU NMOS or CMOS
« Reply #3 on: 18:46, 06 January 16 »
Why this?
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Offline arnoldemu

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Re: Z80 CPU NMOS or CMOS
« Reply #4 on: 19:35, 06 January 16 »
Why this?
Programs which use "OUT (C),0" will not work on CMOS. It doesn't out 0, it outs 255!
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Offline TFM

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Re: Z80 CPU NMOS or CMOS
« Reply #5 on: 19:46, 06 January 16 »
Programs which use "OUT (C),0" will not work on CMOS. It doesn't out 0, it outs 255!


Oh crap! I didn't know! But this can be used to test the CPU version then, right? OUT to a port which you can read again, PSG port f.e. On the other hand if nobody uses CMOS why to bother? But good to know. Thanks for your valuable insights Sir!  :) :)
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Offline arnoldemu

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Re: Z80 CPU NMOS or CMOS
« Reply #6 on: 22:11, 06 January 16 »

Oh crap! I didn't know! But this can be used to test the CPU version then, right? OUT to a port which you can read again, PSG port f.e. On the other hand if nobody uses CMOS why to bother? But good to know. Thanks for your valuable insights Sir!  :) :)
correct.
But I think nobody uses cmos.


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