The "turbo" timings are aggressive and unless you do have all the motherboard manufacturer's recommended parts (e.g. memory) -- the top notch stuff -- I think "turbo" will never work. :wink: I have a board that fails with "turbo".

The unreliable machine's temps seem high and the fan speed seems low. Try setting the Smart Fan Control Method to Disabled (in the BIOS under PC Heath Status section). That should force the CPU fan to maximum and give you an idea if the cooler needs to be reseated/replaced.

Yeah looks like your temps are too high. Try the fan thing and if that does not work try re-seating the CPU. You can hold off on the new PSU for the moment.

I've replaced the cooler with a giant copper thing with heat-pipes and a transparent fan with blue LEDs (a slightly tiresome process since you have to remove the motherboard); the temperature went down by about six degrees, but a medium-sized four-threaded SNFS linalg job using msieve-1.33 still failed weirdly (ran to 157% complete, then submatrix-is-not-invertible):

[code]
Mon Feb 25 00:29:06 2008 matrix is 2368013 x 2368229 (653.8 MB) with weight 164779638 (69.58/col)
Mon Feb 25 00:29:06 2008 sparse part has weight 147700924 (62.37/col)
Mon Feb 25 00:29:06 2008 matrix includes 64 packed rows
Mon Feb 25 00:29:06 2008 using block size 65536 for processor cache size 4096 kB
Mon Feb 25 00:29:30 2008 commencing Lanczos iteration (4 threads)
Mon Feb 25 00:29:30 2008 memory use: 687.4 MB
Mon Feb 25 14:58:23 2008 lanczos error: submatrix is not invertible
Mon Feb 25 14:58:23 2008 lanczos halted after 58838 iterations (dim = 3720589)
Mon Feb 25 14:58:23 2008 linear algebra failed; retrying...
Mon Feb 25 14:58:23 2008 commencing Lanczos iteration (4 threads)
Mon Feb 25 14:58:23 2008 memory use: 687.4 MB
[/code]

~65°C still seems a bit warm to me, but I don't know if that temperature is too high for a core 2.

Does the CPU-fan run at maximum speed? (if not, try to increase it's speed, there must be an option in the BIOS-setup somewhere)

Does the case have fans to get cool air into the case? (a heat-piped copper heatsink sounds good, but it won't work properly if the air around it is boiling)

Have you tried a threaded run on the same mid-size number with an earlier version of msieve?

(one more weird idea: Doas the linalg still fail when you [i]underclock[/i] the cpu?)

Can we have a recap of the memory and mainboard makes and models -- then we might see what the timings should be.

Please list the voltages again, this time with labels.

With the memory, stress your computer with one stick plugged in, then two etc.

When you fit the heatsink do not use too much grease. You need good heat transfer not insulation. The idea is to remove pockets of air which heat up. Use a good quality grease. :smile: