Author Topic: Memory problem? with a 6128  (Read 696 times)

0 Members and 1 Guest are viewing this topic.

Offline angelcaio

  • CPC664
  • ***
  • Posts: 59
  • Country: es
  • AMSTRAD CPC-464
  • Liked: 15
Memory problem? with a 6128
« Reply #10 on: 07:08, 11 May 18 »
Interesting !
In a 6128, the RAM is made of 64k x 1 bit slices.
That would mean that the device handling bit 0 on the base ram is failing for some locations

I guess that your test is only checking the base RAM from 0x4000 to 0xFFFF ?
Can you see the dots that should be there is you only poke &01 to the failing address is the C000-FFFF range ?
Thanks for your interest.
Yes, only from &4000 to &FFFF.
POKE &CD71, 1 shows nothing on the screen, and PEEK (&CD71) gets 0
POKE &CD71, 2 does show a point, and PEEK (&CD71) shows a 1.
Same for the other addresses.


Enviado desde mi iPad utilizando Tapatalk
« Last Edit: 07:47, 11 May 18 by angelcaio »

Offline gerald

  • Supporter
  • 6128 Plus
  • *
  • Posts: 1.238
  • Liked: 891
Re: Memory problem? with a 6128
« Reply #11 on: 10:10, 11 May 18 »
Thanks for your interest.
Yes, only from &4000 to &FFFF.
POKE &CD71, 1 shows nothing on the screen, and PEEK (&CD71) gets 0
POKE &CD71, 2 does show a point, and PEEK (&CD71) shows a 1.
Same for the other addresses.


Enviado desde mi iPad utilizando Tapatalk
So the bit 0 RAM is faulty and you should replace IC127 according to the schematic.

Offline angelcaio

  • CPC664
  • ***
  • Posts: 59
  • Country: es
  • AMSTRAD CPC-464
  • Liked: 15
Re: Memory problem? with a 6128
« Reply #12 on: 12:38, 12 May 18 »
Thanks, Gerald.
I was not sure which was the chip that corresponded to the minus significant bit, the one above or the one below
 
I have ordered on ebay:
The KM4164B 15
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.pl%2Fulk%2Fitm%2F263394118792

And many sokets
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.es%2Fulk%2Fitm%2F222677415495

So as not to solder the chip directly,  although I'm not sure if it's the right socket...


Enviado desde mi H60-L04 mediante Tapatalk


Offline Bryce

  • The Hardware Guy.
  • Supporter
  • 6128 Plus
  • *
  • Posts: 10.043
  • Country: wf
  • It's not broken, it just hasn't been fixed yet.
    • index.php?action=treasury
  • Liked: 3379
Re: Memory problem? with a 6128
« Reply #13 on: 13:29, 12 May 18 »
That's the correct socket.

Bryce.

Offline angelcaio

  • CPC664
  • ***
  • Posts: 59
  • Country: es
  • AMSTRAD CPC-464
  • Liked: 15
Re: Memory problem? with a 6128
« Reply #14 on: 16:57, 12 May 18 »
That's the correct socket.

Bryce.
Thanks Bryce.

Enviado desde mi H60-L04 mediante Tapatalk


Offline ibisum

  • CPC464
  • **
  • Posts: 16
  • Country: at
  • Liked: 0
Re: Memory problem? with a 6128
« Reply #15 on: 14:59, 16 May 18 »
I'm preparing to do something similar to this .. and have the same memory chips .. so very  interested in your progress.

Offline angelcaio

  • CPC664
  • ***
  • Posts: 59
  • Country: es
  • AMSTRAD CPC-464
  • Liked: 15
Re: Memory problem? with a 6128
« Reply #16 on: 07:33, 18 May 18 »
I'm preparing to do something similar to this .. and have the same memory chips .. so very  interested in your progress.
Hi, Ibisum. I am waiting for the orders of the memory chip and the sockets to arrive. Besides the desolder  that says aud in the forum
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/repairs-to-a-cpc6128
I found one on AliExpress. I think I'll have them in early June ...


Enviado desde mi iPad utilizando Tapatalk

Offline ibisum

  • CPC464
  • **
  • Posts: 16
  • Country: at
  • Liked: 0
Re: Memory problem? with a 6128
« Reply #17 on: 08:48, 18 May 18 »
@angelcaio Thanks for the ref to that thread, definitely looks like the same symptoms I'm experiencing with my CPC6128 ..  I haven't had the time this week to debug things (not even opened the case yet) but I hope this weekend I will be able to break out the scope and do some debugging .. certainly interested in your results too, so I hope you get it sorted as well.