There are some blatantly obvious things which we’ve proven with this round of analysis today. Higher clock speed memory modules perform better than lower clocked modules with a Core i7, and likewise, lower-latency modules perform better than higher-latency modules. Triple-channel memory configurations will give you more memory bandwidth compared to single-channel or dual-channel configurations. But anyone who knows a smidge about memory knows that these are basic rules that typically remain true with any platform. Our question is, how much performance will you gain by going out of the way to purchase enthusiast-class high-clock / low-latency modules?
Our tests show that Intel’s Core i7 platform, when equipped with triple-channel memory of any sort, has boatloads of bandwidth to utilize. While the platform is only officially rated to handle 1066 MHz DDR3 memory modules, we found in testing that the numbers really start to come alive once you hit the 1333 MHz to 1600 MHz range. Lower than this, and you’ll be taking a slight performance hit. Above 1600 MHz and you start to see performance gains taper off.
In terms of latency, obviously lower is better. If your modules are in the CAS 8-8-8 to 7-7-7 range, you’ll be getting nearly all of the available performance from a Core i7 system. If you manage to go down to CAS 6-6-6, you’ll see a very slight boost, but not enough to really push for. We wouldn’t necessarily recommend modules in the CAS-9 range, as they tend to not be as effective per clock in comparison to lower-latency modules. Case in point, our lower-clocked CAS 7 OCZ modules typically performed on par with our CAS-9 Corsair modules at a 266 MHz higher clock speed.
Interestingly enough, while the Core i7 platform has tons of bandwidth when utilizing its triple channel memory interface, when we broke this by using 1/2/4/5 module combinations, we didn’t see a large drop in performance. Sure, our synthetic memory bandwidth benchmarks went down significantly, but real-world performance was more or less un-affected. For the best Core i7 experience, obviously we would recommend going for a triple channel kit (as they are readily available now, and priced pretty competitively) but if you have DDR3 modules from a previous system, there really is no harm in equipping a Core i7 with modules in a dual-channel configuration, so long as they'll run reliably at the lower voltages of a standard Core i7 memory interface.
Of the kits we’ve tested today, given the price, default clock speeds/latencies, heatsink designs, and overclockability, our modules of choice would likely be the OCZ Platinum XT. They are priced at roughly half that of the Corsair Dominator modules, but delivered almost identical performance and only a smidge less overclockability. In terms of price/performance, these are the ones to grab. Corsair's modules were impressive indeed, but we feel need major price drops to be competitive. Of course, if money is no option, Corsair is likely your best bet. Kingston's HyperX modules both tested out quite well, but were middle of the road in terms of performance. Price wise, they are very competitive, however, and we have no major qualms against them. If it was our money, though, in these times, the more cost-effective OCZ modules simply make the most sense.
Corsair Dominator XMS3 1866 MHz
OCZ Platinum XTC 1600 MHz
Kingston HyperX DDR3 1600 MHz
Kingston HyperX DDR3 1800 MHz