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Memory subsystem performance

A couple of quick synthetic memory benchmarks confirm our 1866MHz memory config is indeed both higher bandwidth and lower latency than our default 1333MHz setup. The A8-3850 with 1866MHz RAM manages more throughput in Stream than any flavor of Phenom II, and its memory latency is comparable.

However, these results also serve as a reminder of how proficient Intel's newer CPU architectures are at wringing as much as possible from their attached memory. The Core i3-2100 manages 5GB/s more throughput with 1333MHz DIMMs—at a 2T command rate, no less—than the A8-3850 does with 1866MHz DIMMs with a 1T command rate. The Intel processors hide access latencies better, too.

These differences are, in part, a result of Intel's use of larger caches with smart data pre-fetching algorithms that appear to make good guesses about what data our tests will request next. Llano adds a somewhat larger 1MB L2 cache per core and a tweaked pre-fetch algorithm, but it has also shed its L3 cache. In the grand scheme, the changes don't appear to add up to much.