(SOLVED) Cpc 464 noise after loading game

[catenaccio]

Hi all,


Issue is that after repair my cpc swapping z80, now some games have a weird behaviour after loading


Take into account that most games work properly, but with some new games like Dawn of kernel, after loading screen game works well, but sound is only a noise, and relay starts working without stopping


Faulty ram or z80? any  idea?

[VincentGR]

Can you try Relentless?
I have the same issue with one of mine.

[catenaccio]

Can you try Relentless?
I have the same issue with one of mine.

Yep, same issue with Ralentless

[VincentGR]

   creepy.

[catenaccio]

  creepy.

hi Vincent, is it happening the same with relay?

[VincentGR]

No, it is fine.

[catenaccio]

Just to know: Is there any posibility that the new z80 trigger this issue? or maybe be damaged?


New z80 is Z84C0020PEC with higher clock speed. The old one was z8400aps

[catenaccio]

No, it is fine.

Hi Vincent, just a quick question, did you change any time your z80? I mean, is it the original?

[VincentGR]

Yes it's original.
I bought it like this and I tried with a new AY, same results.

[catenaccio]

Yes it's original.
I bought it like this and I tried with a new AY, same results.

So I understand that you had to replace your z80 by another one that is the same as the original, right?

[VincentGR]

My bad, only the AY is replaced.
Everything else is default soldered from the factory.

[catenaccio]

My bad, only the AY is replaced.
Everything else is default soldered from the factory.

Ok, ty Vincent

[LambdaMikel]

New z80 is Z84C0020PEC with higher clock speed. The old one was z8400aps

What makes you think that this is a valid replacement for a 4 Mhz Z80*A*?

From the datasheet:

http://www.zilog.com/force_download.php?filepath=YUhSMGNEb3ZMM2QzZHk1NmFXeHZaeTVqYjIwdlpHOWpjeTk2T0RBdmVqZzBNREF1Y0dSbQ==

The lowest frequency that thing can handle is 6 Mhz... (if at all).
There is the NMOS Z084004 which can do 4 MHz.
I would just get a standard Z80A from Ebay...

From the data sheet:

The Z8400/Z84C00 CPUs are fourth-generation enhanced microprocessors with exceptional computational power.They  offer  higher  system  throughput  and  more  efficient memory  utilization  than  comparable  second-  and  third-generation microprocessors. The speed offerings from 6 -20 MHz suit a wide range of applications which migrate software.

Nowhere does it mention 4 MHz...

[catenaccio]

What makes you think that this is a valid replacement for a 4 Mhz Z80*A*?

The lowest frequency that thing can handle is 6 Mhz... (if at all).
There is the NMOS Z084004 which can do 4 MHz.
I would just get a standard Z80A from Ebay...

Ty LambdaMikel, I had doubts about this z80, but right now I am almost convinced that is the cause of this issue

I just tried with that z80 because it was provided by a mate from my country (fast shipping) and my old z80 was dead.

This would be fine?:

https://www.ebay.es/itm/Z80-A-DMA-Z80-DMA-4MHz-NMOS-DIP40-von-STM/311081941531?hash=item486dedba1b:g:VDUAAOSwTmtaqyPW:rk:2:pf:0

[Fessor]

Ty LambdaMikel, I had doubts about this z80, but right now I am almost convinced that is the cause of this issue

I just tried with that z80 because it was provided by a mate from my country (fast shipping) and my old z80 was dead.

This would be fine?:

https://www.ebay.es/itm/Z80-A-DMA-Z80-DMA-4MHz-NMOS-DIP40-von-STM/311081941531?hash=item486dedba1b:g:VDUAAOSwTmtaqyPW:rk:2:pf:0

No, thats the DMA-Controller for the Z80.
You should look after z0840004psc, thats the part-number of Zilog for the Z80A.

[catenaccio]

No, thats the DMA-Controller for the Z80.
You should look after z0840004psc, thats the part-number of Zilog for the Z80A.

Ty Fessor. Does it have to be from Zilog? or this one will work?:


https://www.ebay.es/itm/Z0840004PSC-USED-USADO-IC-DIP40-Microprocessor-8-Bit-Z0840004-PSC-Z-0840004-PSC/323332550554?hash=item4b481f2f9a:g:M3QAAOSwR4JalAm3:rk:10:pf:0

[Bryce]

I doesn't need to be Zilog, but the one you've linked to is a Zilog part. It says: Marca: Zilog.

Bryce.

[catenaccio]

I doesn't need to be Zilog, but the one you've linked to is a Zilog part. It says: Marca: Zilog.

Bryce.

Yep, your are right Bryce, I didn´t see that.


Thanks guys!

[catenaccio]

Solved, z0840004psc installed and working like a charm!


Ty all guys

[LambdaMikel]

Solved, z0840004psc installed and working like a charm!


Ty all guys

Good to hear! Honestly, it was a miracle that you were even able to boot the CPC with the high speed Z80 and do anything with it at all.

[gerald]

What makes you think that this is a valid replacement for a 4 Mhz Z80*A*?

From the datasheet:

http://www.zilog.com/force_download.php?filepath=YUhSMGNEb3ZMM2QzZHk1NmFXeHZaeTVqYjIwdlpHOWpjeTk2T0RBdmVqZzBNREF1Y0dSbQ==

The lowest frequency that thing can handle is 6 Mhz... (if at all).
There is the NMOS Z084004 which can do 4 MHz.
I would just get a standard Z80A from Ebay...

From the data sheet:Nowhere does it mention 4 MHz...

Z84Cxxx are CMOS Z80 and can run from 0Hz ie, no clock to they max rated speed (6 / 8 / 10 / 20)
A 20MHz cmos Z80 can be used from 0.00000001Hz and below to 20MHz 
NMOS version usually requires a maximum 2us low and 200us high clock. Up to it maximum rated clock (2.5/4/6/8)

[LambdaMikel]

Attached.
Check out the MIN values for NMOS / CMOS.


@Gerald, can you explain your comment based on these values in the tables please?

[gerald]

Attached.
Check out the MIN values for NMOS / CMOS.


@Gerald, can you explain your comment based on these values in the tables please?

On the CMOS data sheet you can see that the clock pulse length (be it low or high) is DC ie flat ie 0Hz 
The min clock pulse duration is in line with the max frequency.
Same for the minimum clock period.

On the NMOS the max pulse size of 2000ns for both high and low pulse give a minimum frequency of 250KHz.
The datasheet I have here (SGS) states a 2000ns high pulse and a note for the low pulse : although static by design, testing guarantee 200us maximum.
This is probably due to the use of pre-charge logic within the Z80 data path that mandate a minimum high pulse, while the low pulse can be as long as you which, but (my guess)
1. stopping the clock was not really a practice
2. manufacturer did not bother testing below 250KHz.

[LambdaMikel]

Thanks for explanation, that's great!
Not easy to read data sheets if one is not from the field...


Any idea, if not clock, what caused the problem then with the higher speed Z80 here?

[gerald]

Thanks for explanation, that's great!
Not easy to read data sheets if one is not from the field...


Any idea, if not clock, what caused the problem then with the higher speed Z80 here?

One possibility is that the game having issue used the undocumented OUT (C),0
It behave like a OUT (C),255 on the CMOS version.