Quote Originally Posted by eva2000 View Post
i7 memory quality not only effects frequency head room but ability to run certain timings so you have 10x core i7 cpus where only 5 or 6 of these cpus can do DDR3-2000Mhz at CAS7.

4GB detection usually occurs when vdimm and cpu vtt (uncore) differential balance isn't correctly set to what your core i7 cpu likes.. so play with the vdimm and cpu vtt somewhat. Same improper balance between vdimm and cpu vtt can also cause everest/sandra bandwidth to report lower than it should even if full tri kit modules are detected.

These kits are validated at 1.65v vdimm and 1.6v CPU VTT (uncore) volts.

Right now I'm working backwards for my tests starting with max intel spec'd 1.35v CPU VTT and seeing how my GTs scale as i bump CPU VTT (vdimm is no longer the sole factor determining memory frequency/timing overclocks)!
Beware of RTL (Round Trip Latency) settings up high now also, they might need finite adjustment based on the board's BIOS settings, IMC quality, memory type/settings, and IOH setup . Once you get to this level, the amount of interaction required to get a stable system is rather painful. I recreated your problem on the DFI board last Friday, switched over to the Gigabyte Extreme and RE II now for clocking this memory up.