DDR3-2000+ Memory Kits - Fast but Flawed

A few 3D results...

Let’s take a quick look as to how 3D benchmarks such as 3DMark Vantage, 3D Mark 06 and 3D Mark 05 are believed to be somewhat affected by memory bandwidth. Vista 64 allows us to see how the memory voltages we utilized for Super Pi apply to a 64 bit OS when all 6GB of memory is fully mapped.

No major gains here in 3DMark Vantage as we have a 100-point difference between CAS6 1836MHz and CAS8 2294MHz.. Voltage wise, we see the need for an elevated idle voltage in Vista due to increased voltage droop under load with 6GB fully mapped. The actual load Vdimm in these benchmarks is exactly the same as what we used for Super Pi 32m under the XP operating system. 

3D Mark 06 scores more consistently run to run than Vantage and seems to prefer the tighter CAS latency of 6, giving a 400 point boost.

Switching over to XP for 3D Mark 05 we find that the GPU benches are not overly sensitive to CAS or memory bandwidth. The best overall scores come when using the 20X Uncore multiplier on our 920 CPU (one below the CPU core multiplier). Using higher Uncore multipliers than the CPU core multiplier actually resulted in lower average results for 3D Mark 05, due to the additional hold times asserted by the IMC to the clock crossing process. This performance offset can be seen in BIOS via the increased Round Trip Latency values. In essence you get faster L3 cache performance while the IMC slows down memory bus transfer times to levy the increased performance on the other side of the bus; giving up one for the other. Bottom line here is that higher Uncore frequencies don't really offer anything exciting in any benchmark that reads or writes more data than the CPU cache can hold. As an example running a 23X Uncore multiplier results in a 15ns shift for the worse in Round Trip Latency which cannot be reclaimed with the current range of settings availble withn the EVGA BIOS. Higher Uncore frequencies may appear attractive at first approximation, but they're not always best in every scenario.  

Using CAS 6 also resulted in the GPU tests of 3D Mark 05 failing to pass at 229 BCLK regardless of voltages, while running 2294 MHZ CAS 8 with the same Uncore multiplier passed without a glitch.