Investigating Sandy Bridge Memory Scaling

Intel's Second Generation Core processors, based on the Sandy Bridge architecture, include a number of improvements over the previous generation's Nehalem architecture. We’ll be testing one specific area today: the improved memory controller. Current Sandy Bridge based processors officially support up to DDR3-1333 memory. Unfortunately, due to changes in the architecture, using faster rated memory (or overclocking memory) on Sandy Bridge via raising the base clock is extremely limited. Luckily, there are additional memory multipliers that support DDR3-1600, DDR3-1866, and DDR3-2133 memory. Some motherboards include support for even higher memory multipliers, but we’ll confine our investigations to DDR3-2133 and below.

Since Sandy Bridge is rated for up to DDR3-1333 memory, we will start there and work our way up to DDR3-2133 memory. We'll also be testing a variety of common CAS latency options for these memory speeds. Our purpose is to show how higher bandwidth memory affects performance on Sandy Bridge, and how latency changes—or doesn’t change—the picture. More specifically, we’ll be looking at the impact of memory speed on application and gaming performance, with some synthetic memory tests thrown into the mix. We’ll also test some overclocked configurations. So how much difference will lowering the CAS latency make, and does memory performance scale with processor clock speed?

Back when I originally envisioned this comparison, the price gap between DDR3-1333 and DDR3-2133 memory was much wider. A quick scan of Newegg reveals that a mere $34 separates those two 4GB kits. Below is a breakdown of the lowest prices (as of 7/16/2011) for various memory configurations.

4GB 2x2GB Kits
DDR3-1333 CL9 $31
DDR3-1333 CL8 $40
DDR3-1600 CL9 $40
DDR3-1600 CL8 $41
DDR3-1333 CL7 $45
DDR3-1600 CL7 $50
DDR3-1866 CL9 $60
DDR3-2133 CL9 $65


8GB 2x4GB Kits
DDR3-1333 CL9 $58
DDR3-1600 CL9 $66
DDR3-1333 CL7 $75
DDR3-1600 CL8 $80
DDR3-1866 CL9 $85
DDR3-1600 CL7 $115
DDR3-2133 CL9 $150

You can see from the above chart that balancing memory clocks with latency results in some interesting choices, particularly on the 8GB kits where price differences are a bit larger. Is it best to go with a slower clock speed and better timings, or vice versa, or is the optimal path somewhere in between? That’s the aim of this article.

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  • Rajinder Gill - Friday, July 29, 2011 - link

    LOL!

    Caught with your pants down there sir.
    Reply
  • Isaac the k - Tuesday, August 02, 2011 - link

    Memory above DDR3-1333 is plentiful and cheap.
    Sandy Bridge benefits from the bump up to 1600.
    Mobo's all can handle the higher spec'ed memory.

    WHY IS INTEL SPEC'ING THE NEW I7's FOR 1333 INSTEAD OF 1600 BY DEFAULT?

    I don't want to have to futz with my BIOS just to get my memory to run at STOCK timings!
    Why the HELL are they crippling the basic utility of their chips??

    I grant you, it isn't a major increase in performance, but why set the ceiling so low? why not set it higher and let the mobo manufacturers choose what their boards are compatible with???
    Reply
  • shriganesh - Wednesday, August 24, 2011 - link

    This article is thoughtful and very good news for mid-end to high-end system builders :)
    There's absolutely no need to pay extra for those faster and better memory modules!!
    Reply
  • ryedizzel - Tuesday, September 20, 2011 - link

    Thank you very much for this article. I have been memory shopping for a couple days now and debating on different memory speeds vs. latency vs. price. I wish I had the lab setup to test them all. Thanks again! Reply
  • James D - Monday, November 28, 2011 - link

    On each speed type (1333, 1600, 1866 etc.) you used only slightly different timings! For example for speed 1333 Mhz you had:
    1) 7-7-7-18
    2) 8-8-8-18
    3) 9-9-9-18
    In this case of course you won't get much different results! Don't you know that changing CL and other timings you can change tRAS timings which is the minimum number of clock cycles needed to access a certain row of data in RAM between the data request and the precharge command.
    OF COURSE you won't get big difference if you didn't change tRAS! If you lower all other timings then most likely you can decrease tRAS which also will increase performance.

    Please rebench all these with slightly different all types of timings. It means a lot for results.
    Reply
  • poohbear - Saturday, December 17, 2011 - link

    Thanks for running the gaming benchmarks @ 1920x1080 to show us practical results (ie there were none!). i hate it when they run these benchmarks @ 800x600 or some nonsensical low resolution to show us a difference that we really could care less about in 2011. Reply

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