Performance in synthetic memory benchmarks doesn't always carry over into the real world, but given our focus today, it's good to get an idea of the bandwidth and latency associated with each configuration.
It should come as no great surprise that faster memory yields greater bandwidth in a synthetic memory test. With the 965 Extreme, there's a healthy jump in bandwidth as we step up the memory speed ladder. With an overclocked base clock, our Core i7-920 keeps up with the Extreme when running memory at 1333 and 1600MHz, too. However, the 920 is notably slower when both processors use 1066MHz RAM, no doubt because the 965 Extreme's memory controller runs a little faster than that of the 920, as does its L3 cache. This difference in memory controller speed appears to be negated when we overclock the 920's base clock to 200MHz, which brings the processor's memory controller and L3 cache up to the same speed as the Extreme's with 1600MHz memory.
Focusing our attention on the 920 with 1066MHz memory, moving from 7-7-7-20 to 9-9-9-27 timings costs about 1GB/s of bandwidth. Lopping off a memory channel drops bandwidth by a further 4GB/s, which doesn't bode well for our dual-channel config. However, it is worth noting that our dual-channel config delivers three quarters the memory bandwidth of a triple-channel setup with just two thirds the number of channels.
As you might expect, faster memory also yields lower access latencies. Here our 920's overclocked base clock isn't enough to catch the 965 Extreme, despite the fact that both should be running their memory controllers and L3 caches at the same clock speed. The difference in performance between 1066MHz DIMMs with 7-7-7-20 and 9-9-9-27 timings is quite a bit larger here than it was in the bandwidth test, too.
By far the most curious result in this lot is that of our dual-channel config, whose access latencies are quite a bit lower (a nanosecond is a relative eternity in the GHz world of the modern PC) than those of our triple-channel equivalent. There might yet be hope for our dual-channel config.