Have you tried more MCH core voltage when going for 500 FSB on the 5:6 divider?
For my run I used 1.45v, but I'm not sure what the minimum I'd need for that is, I just guessed and it ram fine. We have different boards but it may be worth trying.
Also from what I've seen of eva2000's benching on the EP45-Extreme (found here http://i4memory.com/f90/gigabyte-ga-...0-review-8339/), it's pretty damn fast for a P45 board. At what appear to be looser ram & chipset settings than my M2F it appears to be about 15 seconds faster. I'd like to see a side by side comparison of the EP45-Exteme and the UD3P, as I have a feeling the UD3P is going to be slower clock for clock, as it appears to be a more FSB oriented board. Perhaps though with the right chipset tweaks, the A34 rev. chipset may even pull ahead.
What is also odd about the gigabyte boards (EP45-Extreme & UD3P) is that they can run PL9 at 1:1. With an Asus board you can only run PL10 minimum. It may just be different tRD nomenclature though, who knows.
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