Prime95 Rounding Errors on Stock Q6600...but memtest86 passes

[Gerbil333]

Specs:

Asus P5K-E
Q6600 (G0)
G.Skill 4GB (2x2GB) DDR2 800
Radeon X800 XL 256MB
Corsair 520HX PSU
SB Audigy 2 ZS
WD 74GB Raptor
Samsung 500GB
Vista Business 64-bit


I just put this machine together yesterday. Prime95 spit out a rounding error on the 4th thread after just 4 minutes. I increased the DDR voltage from Auto to 1.9V (1.8 should be stock) and ran memtest86+ v1.55 while I was asleep, which surprisingly detected 4095MB--I didn't know that was possible for 32-bit apps. Anyway: Zero errors in over 8 hours (almost 11 passes).

I thought I'd fixed it, so I ran Prime95 with rthdribl.exe (a 3D HDR demo) for over an hour. Prime95 did okay, but rthdribl crashed. It can't be the video card as I've been using the same card flawlessly for almost 3 years. I ran Prime95 again later, no changes, and the 2nd thread produced another rounding error after 11 minutes.

I just increased the Q6600's Vcore to 1.30V in the BIOS and and disabled something called "Transaction Booster." Prime has been running okay for 10 minutes...

Ideas? Could it still be the RAM? Bad motherboard, maybe? I've never had a bad processor before.

Edit: Temps are fine. The CPU idles below 30C and hovers around 41-43C under full load.

 

[Thor86]

Set the vcore to Auto, and memory to 2.0 and nbvcore to 1.55 and try prime95 testing.

Just because Memtest is stable without errors, it doesn't mean it is Windows stable.

 

[Gerbil333]

I'll try that next if the current settings don't work. Prime95 has now been running for 1.5 hours.

 

[LOUISSSSS]

i say put vcore at 1.3v and vram @ 1.9 or 2.0 (+.1 or +.2_ from 1.8 default in bios. then try to run your q6600 at stock speeds of 9 x 266

 

[Gerbil333]

That's exactly what I'm running now. Did I choose a picky hardware combination? I've been building computers for almost a decade and so far, this has to be one of my most troublesome personal machines. I can blame Vista for much of that. I'm considering going back to XP :|

Edit: It finally failed after 2 hours, 10 minutes. Back to the BIOS.

 

[Thor86]

Please don't blame Vista for your hardware testing woes. OS has nothing to do with stability testing. I know I run both Vista Ultimate 64bit and XP Pro 32bit and both oc the same on the same hardwares.

Again, please use my suggested voltages and work from there.

 

[Gerbil333]

Thor,

I am not at all blaming Vista for hardware trouble. I am simply not a fan of Vista (I'm sure it will get better, but I will save that rant for the OS section).

Anyway, after trying all different voltages and BIOS settings to no avail, I swapped my G.Skill 2x2GB DDR2 800 for my girlfriend's Samsung 2x1GB DDR2 667 and that appears to have fixed the problem: Prime95 has been running for almost 20 hours

I'm surprised memtest86 caught nothing.