Yeah 1T performance really is nice on the 680i.
However, you can run DDR1000 @ CAS 4 with same or fewer voltage... and atleast on my old P965 it was quite fast



Couldn't run 1T higher then ~700 or so but that was just using 2,2V which is perfectly ok for 24/7 use
I will be having my X38 here soon so I'll check back.

About Intel and 1T, the Abit IP35 Pro can run 1T up to ~1000 (so I'm hoping the X38 QuadGT can do it as well). However, the performance gain isn't as high as with nvidia.