Hello
Main board GA-X79-UD3 with two 680 GPUs
Debian10 Linux,
kernel 5.10.0-19-amd64
OpenGL 4.6.0
nvidia driver 470.141.03
------------------------------
Months ago, following updating/upgrading of amd64, the GPUs, while
rendering correctly, became unable to run classical molecular dynamics
simulations. Launching a minimization with software NAMD with both GPUs or
with one of them (by software or even by removing one GPU)

namd2 +idlepoll +p12 +devices 0,1 min.conf
namd2 +idlepoll +p12 +devices 0 min.conf
namd2 +idlepoll +p12 +devices 1 min.conf

NAMD organizes the simulation correctly but at the stage of starting the
computation, accessing memory, a crash occurs with error

TCL: Minimizing for 3000 steps
> FATAL ERROR: CUDA error cudaStreamSynchronize(stream) in file
> src/CudaTileListKernel.cu, function buildTileLists, line 1136
> on Pe 4 (gig64 device 0 pci 0:2:0): an illegal memory access was
> encountered
> FATAL ERROR: CUDA error in ComputeBondedCUDA::forceDoneCheck after polling
> 48 times over 0.005047 s on Pe 8 (gig64 device 1 pci 0:3:0): an illegal
> memory access was encountered
> FATAL ERROR: CUDA error cudaStreamSynchronize(stream) in file
> src/CudaTileListKernel.cu, function buildTileLists, line 1136
> on Pe 4 (gig64 device 0 pci 0:2:0): an illegal memory access was
> encountered
> FATAL ERROR: CUDA error in ComputeBondedCUDA::forceDoneCheck after polling
> 48 times over 0.005047 s on Pe 8 (gig64 device 1 pci 0:3:0): an illegal
> memory access was encountered
> [Partition 0][Node 0] End of program
>

"illegal memory access" is a software error (as also proven by using
alternatively one of the two GPUs) that escapes all my attempts at
unraveling its origin. I had no clues from NAMD forum. Hope here.

Thanks for your kind attention

francesco pietra

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