Core i7 Memory Speed/Timings Performance

[Denithor]

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Conclusions:

Intel has made a system that for the most part alleviates the need for more memory bandwidth. Three channels of DDR3 means we're saturated with it from the word go, and for the most part spending big money on faster performance memory has a unnoticeable effect.

For games, it does nothing in the real world because the bottleneck is firmly elsewhere: either the threading capability of the game, the clock frequency of your CPU (not the Uncore) or the graphics subsystem. For other things, we're still limited for stuff like IO and storage bandwidth - so while people complain about memory use, having programs use up a big chunk of 6GB (or more) benefits performance because we're not limited by measly hard drives.

In the one important scenario - multi-tasking - the performance benefits are more considerable, so if you're heavily into running many things at once (partly what the Core i7-X58 combination was designed for) then there is likely a performance benefit in store for you.

Basically, we feel the best advice is don't go crazy because the benefits in the real world are generally not there and are better spent elsewhere. Buy memory that supports your CPU overclocking: but even if you run a base clock of 200MHz on a 6x multiplier from a Core i7 920, the memory can run at 1,200MHz so you don't need the full 1,600MHz.

For the most part, increasing the CPU Uncore frequency that includes the memory controller will give a considerable jump in performance, just like performance memory alone will - the difference is, CPU Uncore frequency is effectively free. A Core i7 920 CPU will run this at 2.13GHz at stock, but increasing its base clock to 180-200MHz will increase it to between 2.88GHz and 3.20GHz, which we've seen demonstrate a performance improvement as well.

Only those looking for records will want those extra half frames per seconds and second or two in benchmarks, meaning every ounce of frequency and timing in a system is important, but this obviously isn't limited to Core i7. While the occasional willy waggling 3DMark might be entertaining, it's not how most of us spend the day using our PCs.

Uncore speed & memory timings had more impact across the board than raw memory speed. And even those impacts were minimal at best, mostly seen in memory benchmarks rather than real-world apps.

So if you're trying to figure out the optimal OC for your shiny new i7, aim for higher BCLK with a lower CPU multiplier to maximize the uncore bandwidth.