Since Intel do not recommend to use over 1.65v as memory voltage in Intel x58 chipset, producers made several steps in order to raise the memory frequency.
Now high-speed memory , which works in the three-channel configuration together with Nehalem reached the clock frequency 2 GHz with aggressive timing (9-9-9-27) and low voltage.
G.Skill also presented today its version : PI black for Intel core i7/Intel x58 express. The modules sets have the volume 3 and 6 GB , function at 2000 MHz frequency with 8-8-8-21.