I’m the user in question. The system is a Core i7 920 OCd to 965 speeds keeping the memory speed to the rated 1333MHz.
For a single GTX280 in this system:
[codebox]hpc-user@gpu-hpc:~$ bandwidthTest --device=0 --memory=pinned --mode=quick
Running on…
device 0:GeForce GTX 280
Host to Device Bandwidth for Pinned memory
.
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 5704.0
Device to Host Bandwidth for Pinned memory
.
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 5618.9
[/codebox]
More interesting, for three GTX280s at once:
[codebox]hpc-user@gpu-hpc:~$ bandwidthTest --device=all --memory=pinned --mode=quick
!!!Cumulative Bandwidth to be computed from all the devices !!!
Running on…
device 0:GeForce GTX 280
device 1:GeForce GTX 280
device 2:GeForce GTX 280
Quick Mode
Host to Device Bandwidth for Pinned memory
…
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 17115.1
Quick Mode
Device to Host Bandwidth for Pinned memory
…
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 16859.3
[/codebox]
I believe these numbers (~17GB/s) represent the bandwidth limits of the triple-channel DDR3 system RAM.
For a single GPU, an X38 or AMD 790FX (better) system can come close to the bandwidths reported above, but for multiple GPUs, nothing comes close to the X58/Core i7 combination from Intel.
Details of the numbers MrAnderson42 referred to can be found at:
http://groups.google.ca/group/hoomd-users/…d07a29946215a93