X61 weird RAM problem

[CPC464]

Hi,
I've got a SXGA+ modded T8100 X61 that I've used for years. Last year it developed a strange problem: It began to power off randomly, reching to the point of not being able to start the OS completely. I suspected of the RAM (it had 8 Gb installed), and tried it with only one module: it works flawlessly. But with both RAM slots ocuppied, it shuts down, regardless of the installed memory. It shuts down with 4 Gb in 2x2 configuration, but it works ok with 4 Gb in 1x4 configuration.

I suposse that the board is somehow faulty and I can't do anything about it, but I'd like to keep using it because the difference in performance between the installed T8100 and the older Meroms is noticeable in this machine.

[RealBlackStuff]

Try it with 1 4GB RAM in 1 slot, then the other slot.
Then remove that RAM and try the other RAM in 1 slot, then the other slot.
Do the same with the 2GB.
Is it a bad slot or a bad module?

[CPC464]

Try it with 1 4GB RAM in 1 slot, then the other slot.
Then remove that RAM and try the other RAM in 1 slot, then the other slot.
Do the same with the 2GB.
Is it a bad slot or a bad module?

It boots OK with only one module in the first slot, regardless of 2 or 4 Gb, but I have a couple of X61 and none of them boot with only a module in the second slot, so I can´t test with a RAM module.
Maybe the second slot is failing. First it failed only with 4+4Gb, but worked OK with 4+2. Then failed with 4+2, but worked with 4+4, and now it shuts off after the Windows boot screen when both slots are occupied. (I've tried with linux and the laptop has the same behaivour, Linux starts to boot, but the laptop shuts down abruptly.

The BIOS recognizes all the installed RAM, but it seems that something fails when the computer tries to use it. I suspect of something going wrong with shared video memory when the laptop enters in XGA mode after booting the OS, but I´m not sure about that.

[unixed]

Change the BIOS (F1) boot method from quick to the alternative. Then test all the modules in the first slot to eliminate any bad RAM. Then switch a now known-good RAM module in the first slot and put another now known-good 4GB module in the second slot. It will take a long time to test on startup, but this way you can start to isolate the problem.

[CPC464]

Change the BIOS (F1) boot method from quick to the alternative. Then test all the modules in the first slot to eliminate any bad RAM. Then switch a now known-good RAM module in the first slot and put another now known-good 4GB module in the second slot. It will take a long time to test on startup, but this way you can start to isolate the problem.

I did as said:
- 1st module 2048 Mb OK
- 2nd module 2048 Mb OK
Both modules Test passed without any warning, but only 3062 Mb are tested.

I tested my other working X61(s):
- The one with 8 Gb installed passed the test, but only 768 Mb are tested.
- Another one with 4 Gb installed passed the test, but, like the defective one, only 3062 Mb are tested.
In any X61 I had been able to test the whole memory. All the three units have Middleton Bios installed.

I`ll try the memory test from Hiren´s boot CD, maybe it can detect something.