CUDA problems (Lunatics) / zero status but no finished file

Hello there,

ever since I replaced one of my two 560Ti GPUs with a GTX 660, a relatively large amount of tasks (I guess 20-30%) restart at least once (exited with zero status but no 'finished' file) after encountering this error:

Error on call (cudaMemcpy(PowerSpectrumSumMax, dev_PowerSpectrumSumMax, (cudaAcc_NumDataPoints / fftlen) * sizeof(*dev_PowerSpectrumSumMax), cudaMemcpyDeviceToHost)), file c:/[Projects]/X_CudaMB/client/cuda/cudaAcc_summax.cu, line 239: unknown error

Alright, I checked:

- Hard drive integrity: OK (and no processes interfering with BOINC or SAH)
- DPC latency: OK, consistently below 500 microseconds, sometimes slightly above 500 if BOINC is active.
- Command rate: OK, set to T2.

About the temperature: is 70°C already too hot? Both GPUs and the CPU typically run at 68-74 degrees under full load. According to the information I had, this is well within their specifications.

About RAM Vdd: I can't really check this now, as I want to avoid restarting the machine unless absolutely necessary. Can this be a problem with RAM? Why would that affect only the tasks running on the 660 GPU and not the older, but almost equally fast 560 Ti?

The power supply should be OK as well. The system ran just fine with two overclocked 560 Tis which used more power.
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The problem persists even after I did this:

- reduce CPU speed from 4.3 GHz to 4.0 GHz
- reduce RAM frequency from 1600 to 1333
- disabled XMP
- installed x41zb
- tested GPU with OCCT, no errors, no artifacts

I can't change the GPU core voltage on the 660, the software doesn't allow that. I didn't find any options to adjust Vdd in the BIOS. The 660 isn't overclocked (past its factory-overclocking) and the software doesn't allow me to go lower than the default clock rates, so I can't do this. The error is probably not related to temperature, though. There was one instance of the error shortly after reboot, when temperatures were still much lower.

Just shortly before the installation of the new 660, I disabled hyperthreading because it was recommended by some in this forum. Could that be related?
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Similar problem on my linux box I suspect.

disabling "SLI" and "multiGPU" options eliminated the memcopy errors I was getting. It's worth a try.

Thank you all for your opinions.

I used an old version of MSI Afterburner that couldn't make use of all the functions. With the new one I can indeed adjust the voltage (but can still not turn the fan speed of my 660 above 74% which is strange). But if, as you say, this is already a rather high temperature I'd rather not fiddle with the voltage control unless necessary. However, according to several internet sources, the temperature is pretty much the expected temperature of my card - the Zotac GTX 660 Amp! Edition - under maximum load, maybe a few degrees higher, but that's expected too (multi-GPU system, very demanding CUDA load instead of the game-based benchmarks)

I never enabled SLI to begin with, and also switched to "single display performance mode", but that too didn't help. I've set the process priority to high via the mbcuda.cfg file.

I'm out of time now, but tomorrow I will try switching the cards around and find out if hyperthreading affects the problem or not. The good thing is that the error is relatively benign and that all of the affected tasks I followed eventually successfully validated.
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I never enabled SLI to begin with

disregard my advice, my host just spit out another error matching the description. lol fist one in 3 days though ,compared to 10 -20 per day

So, some new observations:

- Enabling hyperthreading didn't fix or reduce the errors, I still left it on anyways.
- The error rate seems to be lower with x41g so I reverted back. Might be a coincidence, but at the very least, x41zb is certainly not better in that regard.
- Number of tasks per card doesn't matter. I ran only one task per card over the whole night as opposed to my standard two, but the error rate was not reduced.
- I swapped the cards, the error still only affects the 660.
- A temperature issue can now definitely be ruled out, after swapping the cards, the 660 runs at a temperature of 58-61°C.

Also, I didn't find the SLI option to disable it. I didn't connect the cards with an SLI bridge, so it shouldn't be available, right?
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OK, just to be sure, since I don't have any experience with the GTX 660 - the current core voltage is 1.175 V, core clock 1163 MHz, memory clock 1652 MHz, temperature 58-60°C. Is it safe to increase the voltage and what amount would you suggest?
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Unfortunately I corrupted my BIOS due tue a very badly designed BIOS update procedure. Since I probably will not find a way to recover, I must wait a few days for a replacement motherboard. I'm thankful for all your ideas and will continue with your suggestions as soon as possible.
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