Sounds like a problem with the address logic or refresh. On Sun, 30 Oct 2011, Gerrit Heitsch wrote: > 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 list > wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2011-10-31 05:00:04
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