Hello, today I tried to fix th C128 of a friend. The system is unstable and when checked with a diagnostics module (C128/128D diagnotic Rev 785260) it reported 7 chips in the second RAM bank (U46-U52) as bad. To make sure the module works, I used it with one of my C128 and there it reported no dead RAMs, all banks came back OK. The same system had 2 dead RAMs (MT4264) in the first bank already replaced, so I thought that it's just more of the same and they just used a bad batch of RAM back then when making it. Most of the time the MT4264 shows a strange fault when going bad, you get one stuck bit every 256 Bytes, as if one column died. The rest works fine. Well, after replacing all 8 RAMs (U46-U53), the module still reports dead RAM (now U46, U48, U52 and U53). Since I used sockets I can swap the chips around. The fault sometimes moves, sometimes it doesn't but any given combination of RAMs (KM4164-12 and U2164) will always give the same fault pattern, no matter how often I run the test. Using any of the RAMs in the lower bank never results in any fault so I think all the chips are good. Then I decided to go for broke and remove one of the RAMs from the upper bank and try again. The RAM test didn't show it as bad. Even removing all the RAM from the upper bank will not show all of them as bad. Does anyone here have any idea about what could cause this type of fault? By now I'm pretty sure it's not the RAM. I would also like to do my own tests from the machine language monitor. Can anyone here give me the address space used by the second RAM bank? I'd like to fill it with a few patterns of my own. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2011-10-30 21:00:37
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