Q: I've been experimenting with overclocking my DDR-2 Pentium 4 system, and also tweaking the memory for higher performance. My question is this: my motherboard has an option for 'memory speed', which is a MHz indicator like '400' 533', 667' etc. This does not seem to have any perceptible effect on performance according to my benchmarks. My friend told me this represents the speed of the memory, which makes sense, except that I though that is what the FSB measurement was for. Can you clear this up for me?

A: The setting you describe controls the internal speed of the memory. Assuming you are using an 800MHz FSB Pentium 4 chip, your system's FSB speed is 400MHz DDR (200MHz). Your DDR2 memory is probably rated for a higher speed though, either 533 or 667MHz DDR (266 or 333MHz). The setting in question allows the memory to run at its full rated speed internally while communicating with the processor at the default 400MHz DDR FSB speed. If you had DDR2-533 memory, choosing the '533' setting would set a memory speed ratio of 2.66, causing your memory to run at 533MHz DDR internally while the FSB remained at 400MHz DDR.

As for the settings having little effect on performance, this is not surprising; internal memory speed settings above FSB speed have very little to do with performance in recent Pentium 4 chipsets. they have a slightly larger effect on Athlon 64 performance and early returns suggest that internal memory speed has a very significant effect on dual-core Pentium D processors, but it's unlikely to make much of a difference either way to your particular system. You may find that reducing the internal memory speed makes overclocking easier though.