Gremlins with 975XBX and CM2X1024-5400C4

[Diogenes67]

I have a Core 2 Duo E6700 2.66 MHZ in an Intel 975XBX v305, 1487 BIOS with four modules of Corsair CM2X1024-4500C4. Dual boot XP 32 and WIN7 64. Two modules are a matched pair, the other two were purchased individually. Settings have been either the motherboard defaults of 5-5-5-15 1.8v or a manually set 4-4-4-12 at 2.1v. I'm generally running it at 533 MHZ and overclock to 3.0 MHZ with the Intel Desktop Control Center. I have been running this setup for over two years with no problems.

 

Several days ago it wouldn't POST. I tracked the issue to one of the individually purchased modules which, if present in any slot, prevented POST. The system booted with the remaining three modules. I thought I had the problem solved and removed the balky module.

 

As a precaution I ran MEMTEST on the other three modules in XP, testing each individually at default settings. Each threw numerous errors, two with more than 100 each over two passes. One module would not complete a single pass without numerous errors and then spontaneously rebooting. I couldn't test the fourth as it wouldn't POST. I reinstalled the three modules and the system booted normally. It appears to be stable. However, the fourth module still prevents POST.

 

Then, with three modules, I ran Win Memory Diagnostic twelve hours and Prime95 four hours. No errors. I don't have a second board or other RAM to continue testing.

 

Any suggestions? What do you recommend? I'd like to get back the fourth module for dual channel and WIN7. Should I RMA all four or only the single stick that is the Showstopper? Is MEMTEST so sensitive that it reports errors without real world consequence? What settings should I be using with three modules? Should I drop to two? Thanks.

[vinark]

There is a bug on some mobo´s whereby memtest errors when legacy usb is enabled in the bios.

[Diogenes67]

Thanks...that was it. I disabled legacy usb and ran memtest for four hours. No errors. Now I can RMA the bad module and be good to go.