| Posted By
Phoenix
on 2025-10-15
13:59:41
 |  RAM issue?
Guys, a bit of help would be desired..
I've been suspecting some problem with my +4 a while ago, some titles seldomly had sound issues and random crashes, but it was not really consistent and you can never know for sure if it's loading problem, capacitors not yet warmed up or some other factors like the SID card in the system, but now I am getting a weird evidence.
I noticed that some RAM addresses in my under development game (yes, Dune +4 is still in works  ) simply hold different values in my +4 vs Yape and P4emu. I am still looking at it, but could not find any reasonable SW cause (difference in the middle of the RAM, ~80 bytes at e.g. $63a8)
I wonder if there's any way / proggy to test my machine for hardware errors without external modules or custom ROM? Or if extra tools are needed, is there anyone here who could help me please with the testing (and may be also fixing)?
Thank You my friends
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Posted By
gerliczer
on 2025-10-15
15:37:57
| Re: RAM issue?
There is a reason why such test programmes are usually run from ROM. RAM, especially if it is suspected to be on the verge of giving out its soul, is seldom a good choice to run tests from. They could corrupt results or cause crash during testing, so the tests wouldn't produce any meaningful result. Someone surely could lend you a Diag264 cartridge.
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Posted By
BSZ
on 2025-10-15
17:32:37
| Re: RAM issue?
@Phoenix: If you think the error is around $6000, you can do a simple test: enter the MONITOR, and fill the memory:
F 1000 7FFF 00
Then leave the machine like that for an hour or two. Then a simple check:
C 1000 7FFE 1001
If you do not receive notification of different data, repeat the test by filling the memory with $FF. (This could go up to $FCFF, but the TEDMON does not compare good under ROM.) There is no point in testing with other values, as each bit in the machine's RAM has its own chip. (If this is really a plus/4.  )
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Posted By
Phoenix
on 2025-10-15
18:54:58
| Re: RAM issue?
Thanks BSZ, I was thinking about a simple ASM routine, but this is even easier, I must admit
Gerliczer, do you have such a cartridge? I indeed hope someone can offer help with it, and maybe replacing the RAM if faulty. They are soldered to the board if I am not mistaken, and I don't want to ruin the PCB with my epic skills.
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Posted By
Chronos
on 2025-10-16
03:55:54
 | Re: RAM issue?
In my case the Ram issue finally turned to be a TED issue.. I've tested it with Donkey Kong by Tcfs (Excellent diag program ) My rams are socketed, replaced it and the issue was the same, about 10-20 minutes runtime, the program crashes.. Finally I've replaced the TED and the problem is gone, even with the former memory modules...
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Posted By
SukkoPera
on 2025-10-16
07:43:51
| Re: RAM issue?
Interesting... If that TED has an issue with the memory refresh logic, maybe it will still work on a machine with SRAM (see Hannes512).
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Posted By
Chronos
on 2025-10-16
12:51:11
| Re: RAM issue?
We're talking about forty years old hardware, designed for five years. Anything can happen guys...
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Posted By
Phoenix
on 2025-10-16
13:48:14
| Re: RAM issue?
>>We're talking about forty years old hardware, designed for five years.
Considering that it's aging quite well tho..
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