Well it does seem people have had better luck with overclocking C2Ds on this board than the quads, but there are definitely some quirks and nuances to this board that can simply be hit by an unlucky setting. I do have to use Memtest to get stable as I mentioned in one of my prior posts (runs on startup), although not for tRFC; for reference, the BIOS auto setting seems to result in 68T for my memory. I'm only using 4GB, though, but I do agree with your intuition about the 8GB problem being related to timings somehow. I am glad we have tools at our disposal to improve our chances with relatively immature hardware, certainly helped me out on this one.