I have made a Thread about this using a 680i board. CL3 vs CL4 vs CL5 + 1t vs 2t.
Results were all very similar, though 4-4-4 did not have any shining results, it was probably the best average with 1t, though it's not acheivable with some current intel chipsets, I am to beleive it is possible with the X38?

