CPU - C2D E8400 Mobo - Asus P5K Memory - 2x1GB DDR2 1066
A question I have is that the CPU FSB is 1333, but the mobo spec says 1333/1066. Whats the deal, do I need 1333 speed memory or will 1066 give me a 1333 FSB?
The 1333 MHz figure is the quad pumped FSB, so it's effectively 1333 Mhz, but in actually 333 MHz (1333 ÷ 4). So you only need DDR2-667 for running at stock speeds.
As for motherboard memory standards, that's just marketing and pretty much meaningless. The FSB runs in accordance to what the processor is supposed to.
/*------------- <cut n paste> -------------*/
Formulas for Intel platform @ 1:1 settings: (base FSB speed is SDR, or single data rate)
c x [Base FSB speed] = CPU speed (c = CPU Multiplier)
2 x [Base FSB speed] = RAM speed (DDR: double data rate)
4 x [Base FSB speed] = FSB speed (QDR: quad data rate; Effective FSB speed)
On Intel platforms, running the RAM higher than a 1:1 ratio with the CPU is, for the most part, useless, so don't bother trying to do so. If the BIOS does it for you, just let it. All you need is a 1:1 config, though. Here's some possible clock speeds (as always with OC'ing, your results will vary):