Let’s now move on to the impact of the memory clock and timings on performance. For each platform we checked performance with DDR3 clocked at 800, 1066, 1333 and 1600 MHz as well as the following timings where supported: 7-7-7-19, 8-8-8-20 and 9-9-9-24. We also added, for Sandy Bridge, tests at 1866 and 2133 MHz, with timings of 9-9-9-24 and 8-8-8-20 (uniquely at 1866 MHz).
Latency Starting with latency, measured with Aida64 as before.
It’s interesting to note that the memory controller lag on the Gulftowns makes itself felt above all with DDR3-1333 and 1600 where the advantage in favour of the Core i7 975X is higher.
It is above all important to note that in contrast to DDR and DDR2, the clock is always more significant than the timings. This is true across all the platforms, with a single exception: between DDR3-1333 9-9-9-24 and DDR3-1066 7-7-7-19 and this only on Core i7 platforms on LGA1366. Note that we drop below 40ns on the Sandy Bridge platform at 2133 MHz.
Lets move on with the mono-threaded bandwidth readings taken with Aida64.
In terms of bandwidth, it makes sense that the clock should count more than the timings, but perhaps not as much as you might think. Here we limited all our processors to just one thread, which brings out the impact of timings on bandwidth. The socket 1155 processors are by far the most efficient, even at high clocks where the on-chip memory controller doesn’t flag. The 980X is disappointing while the Phenom IIs confirm what we saw when we looked at the impact of memory channels.
Now for the theoretical multithreaded bandwidth readings with RMMT.
At equal clocks, the Core i7 975X dominates the rest of the panel. The Core i7 2600K gives a jump of 11% on the Core i7 860. Note that DDR3 1600 memory doesn’t bring any advantage in terms of bandwidth to the Phenom II X4 965. Although the Phenom II X6 1090T and its new die obtain slightly more, the gain in performance is very slight indeed. A bandwidth limitation can already be felt on the AMD platforms between DDR3-1066 and DDR3-1333. Let’s hope that Bulldozer will correct this issue.