Replacement Z80A CPU

Started by darkhalf, 16:58, 18 May 21

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darkhalf

Unfortunately my recently aquired CPC464 will did not power on. Sometimes screen would scroll random patterns and then stop.


I swapped the Z80A over (from the other CPC464) and all came to life fortunately. Was hoping it wasn't one of the ASIC Amstrad parts!


So now I'm in the hunt for another Z80A. Do you need to use the Zilog ones or can the Sharp ones be used?

https://www.ebay.com.au/itm/372272867554


Does anyone know of a reliable source for these?


I'm in Australia, and freight is a nightmare 60GBP just to get the 464 here due from the UK. Many ebay sellers have complaints of counterfeit chips. I've seen this first hand with CRTC chips. Had one good one, and one fake


thanks
Matt
CPC6128, 2xCPC464, C64, A500

TotO

#1
Use NMOS Z80 CPU to be fully compatible with CPC programs like Z0840004PSC.
I don't know about if the Sharp Z80 are NMOS or CMOS...
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

darkhalf

#2
Okay thanks will dig further


Part number on working 464: MOSTEK MK3860N-4
Dead 464 and my working 6128: Zilog Z8400A PS (380A)


Edit: CPC service manual has IC111 as Z84400 APS
CPC6128, 2xCPC464, C64, A500

RetroCPC

Are you sure the Mostek part number is not MOSTEK MK3880N-4 ?

Anyway, this is a better link for a NMOS Z80A:-

https://www.ebay.com/itm/402782080514?hash=item5dc7aece02:g:-Y8AAOSwSddgbVrT

With ordering from China, you always have the risk of fake parts but the cost of this part its not going to break the bank...

TotO

"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

Bryce

I've bought parts from them in the past too and they were always good. Now if I could just convince them to stop using that non-ESD safe pink foam they use, they would make it higher on my favourites list!

Bryce.

matburton

Quote from: TotO on 17:05, 18 May 21Use NMOS Z80 CPU to be fully compatible with CPC programs like Z0840004PSC.

I've also had to replace a CPU (among other things) and bought a Z0840004PSC.

How can I check it's genuine, i.e. NMOS and not re-badged CMOS? Anything I can do at the basic prompt?

TotO

Quote from: matburton on 21:24, 11 November 21How can I check it's genuine, i.e. NMOS and not re-badged CMOS? Anything I can do at the basic prompt?
I have bought them two times from this seller two years ago and they worked properly:
https://www.ebay.fr/itm/254599020800?hash=item3b4748c100:g:-DwAAOxy63FSvE2K
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

matburton

Quote from: TotO on 22:09, 11 November 21I have bought them two times from this seller two years ago and they worked properly:

How did you know they were genuine NMOS? Were there any checks you performed?

ajcasado

Quote from: matburton on 22:14, 11 November 21How did you know they were genuine NMOS? Were there any checks you performed?

Run any program that uses the Arkos sound engine (for instance adios a la casta), if the sound is OK then the CPU is NMOS. It uses undocumented opcodes that perform different actions in cmos and nmos z80's.
CPC 664

Empiezas a envejecer cuando dejas de aprender.
You start to get old when you stop learning.

TotO

"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

VincentGR

Relentless also has problems with the other Z80, dunno if it is a 128K game though.

GUNHED

Quote from: ajcasado on 22:29, 11 November 21
Run any program that uses the Arkos sound engine (for instance adios a la casta), if the sound is OK then the CPU is NMOS. It uses undocumented opcodes that perform different actions in cmos and nmos z80's.


Which Z80 commands / opcodes are the problematic ones?
http://futureos.de --> Get the revolutionary FutureOS (Update: 2022.03.09)
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ajcasado

I guess that is OUT (c),0, it outputs 0 in nmos and 255 in the cmos version.
CPC 664

Empiezas a envejecer cuando dejas de aprender.
You start to get old when you stop learning.

GUNHED

Quote from: ajcasado on 15:44, 12 November 21
I guess that is OUT (c),0, it outputs 0 in nmos and 255 in the cmos version.
Thank's a lot for that information. Well, I used that instruction too. Good to know in case of problems.
http://futureos.de --> Get the revolutionary FutureOS (Update: 2022.03.09)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2021.12.26)

TotO

"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

matburton

Quote from: ajcasado on 15:44, 12 November 21
I guess that is OUT (c),0, it outputs 0 in nmos and 255 in the cmos version.

Long shot, but is there any way to try this Z80 instruction from basic?

I have a working keyboard but not a working tape drive for this CPC.(The idler tyre has perished)

Axelay

Quote from: VincentGR on 14:06, 12 November 21
Relentless also has problems with the other Z80, dunno if it is a 128K game though.


It's not 128k, only 64k required, was designed to fit in a 16k ROM for the wiki compo.  But it uses the Arkos Tracker 1 replayer, which does use that OUT (C),0 instruction.

GUNHED

http://futureos.de --> Get the revolutionary FutureOS (Update: 2022.03.09)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2021.12.26)

TotO

#19
Quote from: GUNHED on 02:58, 14 November 21
Now  ;) :)
"Oh crap! I didn't know!" Since January 2016! ;)
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

GUNHED

Quote from: TotO on 04:26, 14 November 21
"Oh crap! I didn't know!" Since January 2016! ;)


Your memories are exzellent! Congratulations. I'm happy to know what I did last weekend.  :-\
http://futureos.de --> Get the revolutionary FutureOS (Update: 2022.03.09)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2021.12.26)

TotO

Quote from: GUNHED on 21:44, 14 November 21
Your memories are exzellent! Congratulations. I'm happy to know what I did last weekend.  :-\
Thank you, my own X-MEM. ;D 
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

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