Freeze under mem load with 2GB RAM but not 1GB [SOLVED]

[bk0]

On my amd64 system (athlon x2 4200, asus m2a-vm mobo) my system consistently freezes when I put 2GB ram in it but the freeze disappears when I remove the second 1GB stick. Both modules pass an overnight memtest86 run with zero errors. Switching the modules around doesn't make a difference (ie, having one or the other in makes the machine run fine, with both installed it freezes) nor does running it in single or dual channel mode.

It freezes every time under memory load (ie, when I launch a big java app like azureus) not CPU load. If I only run very minimal applications it will run indefinitely but within a few seconds of starting a big app it will hard freeze every time. Like I said, removing a 1GB stick fixes the problem. I've replaced EVERY component in this machine including the power supply, so I'm confident it isn't a hardware problem.

My questions are:

1) I can consistently trigger the freeze in X but with that I can't see console output, is there any way to persistently save kernel crash messages/dumps so I can get a clue of the cause?

2) Assuming it's a kernel crash, what different options should I enable/disable? I have PREEMPT with PREEMPT-BKL. I do not have console framebuffer enabled. I AM using fglrx with kernel 2.6.21-gentoo-r2 (Radeon Xpress 1250)

[msalerno]

Do you have the high memory support enabled in your kernel?

[bk0]

There is no HIGHMEM option that I can find, I'm assuming because it's 64bit (amd64).

[msalerno]

DOH! You are correct sir.

Check out the kernel hacking section of the kernel. There's an option named "Magic SysRq key"

[mattst88]

I had a problem very similar to this with my Abit NV8 and Sempron 2800. For some reason, when using two sticks of memory (1GB each) I would get random hardlocks. Each stick passes all memtests when alone. Through posting on some other forums, I heard somewhat of a rumor that some AMD64 memory controllers are unstable with two sticks of a 1GB.

I was never able to work it out. I sold one of the sticks to my brother and went about my business with only 1GB.

[paulisdead]

might just be an incompatiblity with your chipset or BIOS. You update your bios yet? Also check your RAM timings and maybe try 2T timing and see if that helps.

Are you using any high end memory that the manufacturer suggests using higher voltages to operate at the advertised speed?

Some mobos just don't like certain types of memory. I had one set of RAM that would pass memtest86+ all I wanted but would bomb out during compiles, switched to different RAM and worked perfectly. Perhaps there's a local PC shop with a good return policy, so you can buy the ram, try it, and return it if you have the same issue. Just be sure to get a different brand of RAM. It might even be a good idea to check your mobo's manufacturers recommended memory modules.
_________________
"we should make it a law that all geeks have dates" - Linus

[bk0]

Manually bumping up the DRAM voltage in the BIOS to 1.9v seems to have fixed the problem (*fingers crossed*). Previously I had it set at 'auto', the economy Patriot RAM I have is listed as 1.8v but apparently needs a little more (or more likely there's some mobo/BIOS bug).

Thanks for the suggestions, I'm glad I don't need to buy new RAM.

[bammbamm808]

[-Craig-]

Same Mobo, same RAM, same problem over here.
I hope increasing the voltage also helps here.

[-Craig-]

Yes, fixed it.