Hi, I have an ASUS board the supports FSB 800 Mhz. My memory is 400 Mhz, however I have 2 slots (Dual). Is this ok ? I mean what speed the memory should be to support 800 Mhz FSB (2 slots of 400 each = support for 800 FSB processor ???). Thank you

Your FSB actually runs at 200MHz, as does your RAM, but your FSB is quad pumped while your RAM is doubled, hence the reason it is called DDR (double data rate). It doesn't really run at 400MHz, it just does twice the amout of SDR (single data rate) per cycle, its all a marketing ploy. The purpose of having dual channels is to try and bring the RAM in sync with the FSB. At 800MHz, you have a theoretical bandwidth of 6.4GB/s, wheras DDR400 alone only has a peak bandwidth of 3.2GB/s (hence the name PC3200), by having dual channels, you bring it up to a theoretical 6.4GB/s, bringing it in sync with the bandwidth availiable to the CPU. Although you never quite get to the 6.4GB/s, you can get pretty damn close.

Hi Adam and thank you for your answer, So if I understood correctly: FSB = 200 x 4 = 800 so 4 sticks of DDR = 200 x 4 = 800 This is what is needed in order to take advantage of the FSB full speed ? Thanks P.D.: 2 sticks of DDR means I use only 2 x 200 = 400 Mhz while the processor can run at 800 ??

No, two channels not four sticks, here: FSB = 200 x 4 = 800MHz (6.4GB/s) RAM = 200 x 2 = 400MHz (3.2GB/s) but there are two channels, so it is doubled again, but it doesn't give you 800MHz, it gives you two RAM channels each with 3.2GB/s bandwidth, thus you get a total of 6.4GB/s.

OK. So if I have 2 empty slots (only 2 sticks out of 4) it means I'm unsing only 1 channel and then 400 Mhz (3.2 GB/s) ? (i.e. not taking advantage of full FSB speed) ? thanx Avi

Each channel has two DIMM slots, you put one stick in each channel. Its usually colour coded, on the Asus boards they use blue and black, put a stick in each of the blue slots and your done.