Intel Sandy Bridge-E Core i7-3960X CPU Review

Author: MAC
Date: November 14, 2011
Product Name: i7 3960X
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Feature Test: DDR3 Memory Channel & Frequency Performance Scaling

From about mid-2003 to late 2008, a dual-channel memory interface was as good as it got on the desktop. However, the LGA1366 platform kicked things up a notch, with the first implementation of a triple-channel memory configuration. Combined with a new integrated memory controller (IMC), Nehalem processors produced gigantic memory bandwidth figures. However, as our tests at the time demonstrated, this additional bandwidth did not necessarily equate to better overall performance since very little consumer-oriented software needed that much memory bandwidth. That is one of reasons why Intel did not hesitate to roll back to dual-channel with subsequent mainstream processors like Lynnfield, Clarkdale, and Sandy Bridge LGA1155.

However, today we are dealing with a new generation of software and a super high-end six-core chip with a unprecedented quad-channel DDR3-1600 memory interface capable of 51.2GB/s of memory throughput. Will this make a difference or is it still just overkill in the consumer realm? That’s what we are here to find out. Simply put, we tested the Core i7-3960X in both dual and quad-channel mode in order to determine whether there were any appreciable performance differences.

As expected, the answer to the above question is that in this case a quad-channel memory interface is overkill, providing miniscule performance gains over a simpler dual-channel configuration. The reason why the results are so close is that a dual-channel DDR3-1600 interface is capable of a theoretical 25.6GB/s of memory bandwith, which is identical to the triple-channel DDR3-1066 interface that was found on the LGA1366 platform…and no one ever said that platform ever lacked memory bandwidth, even when paired with a six-core Gulftown processor.

Since we have already established that the LGA2011 platform has an over-abundance of memory bandwidth, it might seem pointless to test whether higher clocked modules might be helpful, but we gave it a shot anyways.

Obviously, it is not the additional bandwidth that’s responsible for the differences, the slight gains in performance are due to the lower memory latency (46.3ns vs. 51.6ns). So basically, don't feel like you have to rush to ditch your existing memory kits if you want to make a jump to this platform. Using your current dual-channel kits will noticeably impact performance, and if you have a high-end kit it will reach new levels thanks to the enhanced memory overclocking capabilities of the LGA2011 platform.

Now having said all that, there are enterprise and professional workloads that might make proper use of the quad-channel memory interface, but it’s not something your average enthusiast/power user is likely to encounter. It's also possible that it might provide some benefits once multiple PCI-E 3.0 graphics cards are installed since in that scenario the i7-3960X's HyperTransport Link ramps up from 5.0 GT/s to 8.0 GT/s, and the total bandwidth available for the PEG slots jumps from 16GB/s to about 32GB/s. Once those cards are released we will definitely be testing that out.

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