Memory subsystem performance doesn't always track with real-world applications, but it's a good place to start.
And the nForce 780i SLI starts off pretty well, trailing only the 680i in memory bandwidth and latency. The gap in performance is more notable with latency than it is with bandwidth, where the two nForce boards essentially tie. Note that the nForce boards have a particularly large advantage over the Intel chipsets when the latter are confined DDR2 memory, as well.
Memory controllers don't always handle four DIMMs gracefully, so we popped an additional two memory modules into each system for another round of tests. In these tests, we had to back off to a 2T command rate for the nForce and DDR3-equipped X38 systems. This is common adjustment for four-DIMM configurations.
Popping additional DIMMs into our 780i board improves its standing in our memory subsystem tests. It essentially ties the DDR3-equipped Intel chipsets on the bandwidth front while delivering much lower memory access latencies. In the latency test, the 780i is just a fraction of a nanosecond from turning in the fastest overall performance, too.
The following latency graphs are a little indulgent, so I won't be offended if you skip them. They show access latencies across multiple block and step sizes, painting a fuller picture of memory controller performance with each chipset. I've arranged the graphs in order of highest latency to lowest. Yellow represents L1 cache, light orange is L2, and dark orange is main memory.
Nvidia has one heck of a DDR2 memory controller in its nForce 680i and 780i SLI chipsets.
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