FSB / PSB / DDRxxx HELP!

[Xorcist]

Um... I'm confused as hell. It used to be your front side bus times a particular clock ratio would determine your processor speed, and that base number would then determine your memory speed. For example:

100 FSB x 4.5 CR = 450Mhz and your memory would run at 100Mhz

But now, with these new technologies I can't figure out what to buy, let alone how they'll all work together. Here is my dilema. I'm looking at getting a Shuttle AV46N motherboard, which has three FSB settings (Auto, 133, or 100). However the motherboard is rated for 400/533Mhz PSB and up to DDR400 (i.e. PC3200).

Now from what I understand DDR400 works at a 200Mhz x2 (I don't know if that's supposed to be FSB or PSB?). The motherboard only has settings for 100 or 133Mhz? But somehow the processor runs at 400 or 533Mhz? I have no idea what numbers I'm supposed to be matching up!

I think it works like this:

Given a P4 2.4Ghz with a PSB of 400Mhz
100 FSB x 24.0 CR = 2.5GHz and the memory would run at 400Mhz

OR

Given a P4 2.4Ghz with a PSB of 400Mhz
133 FSB x 18.0 CR = 2.4GHz and the memory would run at 533Mhz

But there is no DDR533, so I'm assuming that with DDR400 installed it would only run at 400Mhz (i.e. 133 x 3 = 399). But if that is how it works then the DDR on a 133 FSB only gets read 3 times per cycle rather than 4 at 100Mhz (i.e. 100 x 4 = 400).

Now for starters is this at all correct? It would be great is someone could list some explainitory pages on this subject for me. And secondly, would it be better to sync the PSB with the DDR rating? or is faster better no matter what? I'm looking to build this machine for gaming only, and want the best possible performance. Any insight or suggestions would be appreciated.

[Zanthos]

I actually just ignore all the multiplier settings, I could look up what they mean, but that would be more useless knowledge kludging up my brain

From what I "know"(it could all be wrong)

DDR2100 goes @ 266Mhz
DDR2700 goes @ 333Mhz

P4 2.40B goes @ 2403~Mhz and has a 533Mhz FSB capability
P4 2.40 goes @ 2403~Mhz and has a 400Mhz FSB capability

Basically the aim is to reduce the bottlenecks, for example having DDR3500 which cost you your car, and then throwing it in some board which can *only* handle DDR266, its not worth it.

The FSB is not linked to the DDR speed, the FSB is the main channel of communication out of the CPU to all devices on/connected to to the motherboard(I think, or at least, to all intents and purposes it'll do ).