Single/dual Channel?

[clocker]

So it wasn't just me.

Good.

[lynx]

I think it is mainly that the underlying bus structure and cpu chip simply can't handle the data flow. Remember that although dual channel effectively gives 128-bit bandwidth, the processor still only has a 64-bit data bus.

The Athlon 64 (939 and 940 pin) chips seem to get much higher memory bandwidth with dual channel, presumably because the cpu chip itself has a 128-bit data bus.

As for "more memory always gives better performance", this depends on whether you are using the memory you have at present. If not, Windows will simply use the extra memory as disk cache, and unless you are using a lot of disk-intensive processes the benefits are going to be marginal.