In fact, i can just handle 210fsb not 212 (after some tests, i'm unstable at 212 even with upper voltage ->0.1v

). For my dimms, i chose them by serial number. So my 4 dimms are exactly the same (same serial#), and have been tested separatly without errors.
For timings relaxing, i just read an article about newcastle controller. I this article, we can read that on common bench(3dmark,...) and games (ut2004, farcry...) the results are the quite same between
cpu @250 (1:1) with 3-3-3-8 timing and
cpu@215 (1:1) with 2-2-2-5 (but it seems that it isn't the same results with venice and x2).
With these results, i'm quite disturbed about timing relaxing now

...Nevertheless, I will continue my own tests...