Memory Scaling with Overclocking

What happens when we increase the CPU clock speed on our Core i7-2600K from the default 3.5GHz to 4.8GHz; how will that affect memory performance? To find out, I ran the memory bandwidth tests again comparing DDR3-1333 CL9, DDR3-1600 CL9, and DDR3-2133 CL9 at both 3.5GHz and 4.8GHz CPU clock speeds. I also ran the most bandwidth intensive real-world test along with the least bandwidth intensive real-world test at the overclocked CPU speed to see if the faster CPU clock speed made any difference here as well.

AIDA64 v1.60.1300 - Memory Read (Overclocked)

AIDA64 v1.60.1300 - Memory Write (Overclocked)

AIDA64 v1.60.1300 - Memory Copy (Overclocked)

AIDA64 v1.60.1300 - Memory Latency (Overclocked)

The AIDA64 memory benchmark shows that memory bandwidth does scale with CPU clock speed. Going from DDR3-1333 to DDR3-1600 showed a 14% boost on our stock CPU while showing a 16% boost on our overclocked CPU. Stepping up from DDR3-1333 to DDR3-2133 saw a 33% increase on the stock CPU and a 43% increase on our overclocked CPU. The copy and latency tests showed similar results. What's more impressive is that the write test showed a much larger 15% increase from DDR3-1333 to DDR3-1600 on the overclocked CPU compared to 3% on the stock CPU. Going from DDR3-1333 to DDR3-2133 increased write performance by 22% when overclocked compared to 7% when stock. While it's interesting to see how an overclocked CPU affects raw memory bandwidth, I'm much more interested to see how it affects our real-world benchmarks.

x264 HD Benchmark v4.0 - Pass 1 (Overclocked)

x264 HD Benchmark v4.0 - Pass 2  (Overclocked)

Cinebench R11.5 - CPU (Overclocked)

The extra bandwidth gained with the overclocked CPU doesn't exactly translate into much. The first pass of the x264 test reveals a 7% advantage for DDR3-2133 over DDR3-1333 on our overclocked CPU while the stock CPU shows a 5% increase. The increase for DDR3-1600 over DDR3-1333 is 3% for both our overclocked and stock CPUs. Once we move on to the second pass, there's no discernible advantage for faster memory on our overclocked system. The Cinebench test results are every bit as unimpressive with overclocking as at stock: overclocked or not, faster memory makes no real difference (though the faster CPU clock speed definitely helps a lot).

Graphics and Gaming Final Words
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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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