Some random observations -

RAM
  • In general, a delay skew was needed, with more delay needed on channel A than channel B. Between 400 and 420 FSB best stability comes from Normal skew on both A and B channels. 420-440 needs a 25ps delay on channel A. 440-470 needed a 50ps delay on channel A and a 25ps delay on channel B, my board won't successfully post at higher than 470 so I can't comment above.
  • Memtest is useless for testing skew. As long as the RAM will boot, Memtest will run successfully. Best test appears to be a SuperPI run, the longer the better.
  • Random reboots at idle is a symptom of bad skew.
  • Performance level and clock twist is limited by both FSB and RAM. My RAM (the approved 2*1GB Corsair XMP1600 CAS-7) is happy to do PL-6 at up to 420FSB, PL-7 at up to 440 and PL-8 at up to 470. Clock twist is less easy to narrow down, I seem to be able to run various settings at various FSB and RAM settings. Not much help I realise.
  • The P5E3 Prem in general seems happy to run 1T timings at all FSB settings.

Board
  • vTT (called FSB Term) and vPLL are needed to push high FSB on a quad, with vTT having a greater effect on stability. Between 400 and 420FSB a vTT of 1.2 and a vPLL of 1.6 were needed. Between 420 and 440FSB a vTT of 1.26 and a vPLL of 1.66 were needed. Up to 470 FSB a vTT of 1.3 and a vPLL of 1.7 were needed. I did not feel comfortable running higher voltages than this on a 45nm chip, especially as Intel lists the max safe vTT as 1.35V and many users report killing 45nm chips with vPLL settings of 1.8V.
  • Setting strap to "Auto" is useless, set it manually. The board does not seem to realise that at a higher FSB setting a higher strap is needed, and instead changes strap according to the RAM speed setting you've selected. 333 strap was stable up to about 440FSB, 400 was needed above 440. Be aware that RAM dividers are linked to strap settings so your RAM OCing may suffer somewhat.
  • Board is quite heat sensitive. Aftermarket cooling or directed airflow is recommended - the X48 chipset has the highest rated TDP of all Intel chipsets at ~35W.
  • NB voltage appeared to have little affect on results after 1.4V was reached running 2*1GB. This may change at 4*1GB or at FSB speeds above 470.


Hope that helps