In a recent post (link) I showed that local memory latency is weakly dependent on processor and DRAM frequency in a single-socket Phenom II system. Here are some preliminary results on memory bandwidth as a function of CPU frequency and DRAM frequency in the same system.
This table does not include the lowest CPU frequency (0.8 GHz) or the lowest DRAM frequency (DDR3/800) since these results tend to be relatively poor and I prefer to look at big numbers. 🙂
Single-Thread STREAM Triad Bandwidth (MB/s)
Two-Thread STREAM Triad Bandwidth (MB/s)
So from these results it is clear that the sustainable memory bandwidth as measured by the STREAM benchmark is very weakly dependent on the CPU frequency, but moderately strongly dependent on the DRAM frequency. It is clear that a single thread is not enough to drive the memory system to maximum performance, but the modest speedup from 1 thread to 2 threads suggests that more threads will not be very helpful. More details to follow, along with some attempts to make optimize the STREAM benchmark for better sustained performance.