Overclocking And Under-Latency Results
Only two of the memory kits in today’s round-up are rated at DDR3-2400, while others list DDR3-2133 as their top validated data rate. So how many kits are actually capable of pushing the high mark on our motherboard?
Corsairs 8 GB kit barely exceeded expectations, while RipjawsZ fell slightly below them. In spite of that, G.Skill’s kit is still the fastest among 16 GB competitors.
Ergo our caveats, the first of which is that many Sandy Bridge-E-based processors can’t reliably run at DDR3-2400. Our first Core i7-3960X wouldn’t reach this frequency at any setting, and its replacement is barely any better in this regard (though its higher-attainable core speed does make motherboard testing easier).
The second caveat comes from Asus, which informed us that CPU VCCA (formerly referred to as uncore) voltage probably shouldn’t exceed 1.20 V. According to them, some processors lose stability and may even be damaged at higher settings, while others do not or will not. Ours reached the highest memory settings using 1.20 to 1.25 V.
Our third caveat is that different memory firms use different CPU samples to determine the best settings for their own memory, and those settings might not be right for your CPU. Corsair, for example, included VCCA of 1.40 V in its XMP profile, but wouldn’t overclock well until we dropped it to 1.25 V. Likewise, G.Skill’s 1.20 V XMP VCCA worked perfectly with our CPU, but probably wouldn’t work well with whatever CPU the folks at Corsair used to dial in their profile.
None of the DDR3-2133 samples include VCCA in their XMP profiles, likely because the CPU’s memory controller only needs this adjustment at extremely high data rates.
|Best Timings at 1.65 V|
|Corsair Dominator GT CMGTX8 (4 x 2 GB)||10-12-10-12||9-10-9-10||8-9-8-9||7-8-7-8|
|G.Skill Ripjaws Z F3-19200CL9Q-16GBZHD||8-10-9-10||7-9-8-9||6-7-7-7|
|Geil Evo Corsa GOC316GB2133C9AQC||9-11-9-11||8-9-8-9||7-8-7-8|
|Mushkin Redline 993997||9-10-9-28||8-9-8-9||7-8-7-8|
Corsair has the best DDR3-2400 timings, though this is likely a result of its lower-density 8 GB kit. Our CPU sample, hand-picked for its overclocking headroom, couldn’t handle the larger, higher-density 16 GB kits at this frequency. That also eliminates any DDR3-2400 performance testing, since we’d need at least two devices to compare.
G.Skill takes over from DDR3-2133 downward, its 16 GB kit pushing 1-cycle lower CAS at every tested frequency, compared to competitors.