Benchmarks - SiSoft Sandra, general apps
The hallmark of Sandy Bridge-E's four-channel architecture is meaty dollops of delicious bandwidth. Take away two DIMMs and memory bandwidth reduces by 43 per cent, according to SiSoft Sandra's throughput test. This makes implicit sense and reinforces the need to have four memory modules in an SNB-E system.
Cache and the cryptographic bandwidth is all hunky-dory with four DDR3-1,600 modules installed, too.
And memory latency is roughly the same in both cases. So there's an overriding need to use four modules, right? Read on.
General apps
Now, what's going on here? The number-crunching PiFast test only shows the slightest benefit when jumping from two modules to four.
The all-core CINEBENCH test indicates that two modules are a smidge faster. We ran the test several times and came up with the same result. One explanation is that CINEBENCH's workload is wholly bandwidth-agnostic, and having two modules reduces any minor memory-related overhead, leading to a better result.