Folding Forum

Will cpu speed affect ppd on a gpu? On my system will it help to bump my 2600k from 3.6 to 4.5 GHZ to get more ppd from a 290x GPU? I have 20% cores dedicated to the gpu and the other 80% are crunching on WCG. Will it help on an Nvidia card? Thank you in advance.

Welcome to foldingforum.org, mx500torid.

For the CPUs which are used to support the GPUs, the speed is unimportant. If you fold with a CPU slot or run WCG, the CPU speed and the number of CPU cores allocated are very significant.

The usual recommendation is to use one CPU thread for each (or possibly for every two) GPUs, though I don't recall any specific tests of performance. More than one CPU thread will not help, AFAICT.

CPU processor speed will only marginally affect GPU performance, since the main CPU function is to control the data transfer, which is almost certainly limited by bus bandwidth rather than processor throughput.

Thank you both for the speedy reply.

davidcoton wrote:CPU processor speed will only marginally affect GPU performance, since the main CPU function is to control the data transfer, which is almost certainly limited by bus bandwidth rather than processor throughput.

The CPU is also responsible for managing the checkpoint data, and since that data must always represent the entire protein in the same state, GPU processing is synchronized and temporarily suspended. For most systems, that represents a brief pause, the duration of which is dominated by the speed of your disk subsystem (and also depending on how your system manages the disk cache). CPU speed MIGHT represent a small fraction of that, too, but a small fraction of a small fraction can be neglected.