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).

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  • Black1969ta - Monday, July 25, 2011 - link

    This article ignores a very important factor in choosing RAM, that is overclocking ability, sure the delta between 1333 and 2133 is not very large within the same stick of RAM that is down-clocked but what about a 1333 stick that is overclocked. Can the $50 stick of 1333 perform at 2133 or even 1866, etc... that the $150 DDR3-2133 does with no problem.

    I would like to get a i7-2600K and overclock it to 4.8GHz, but I wanted to know the cheapest stick of RAM that will allow that with no compromise, this article doesn't tell anything useful, sure a good expensive stick is a good expensive stick at any speed, but what about a cheaper stick?
    Reply
  • compudaze - Monday, July 25, 2011 - link

    That's a chance you just have to take youself. Just because my brand X model Y value DDR3-1333 ram will run at DDR3-2133 CL9 at 1.65V doesn't mean that you're guaranteed to get the same results if you buy the same make/model value DDR3-1333 ram. Same with CPU's & GPU's. Reply
  • xsilver - Friday, August 05, 2011 - link

    but for someone not in the know, how well generally does 1333 ram overclock. Some generations the bargain basement ram has no headroom at all and some generations, most basement ram has enough headroom to get where you need.

    Also, as an addendum, maybe you could also test ram size scaling as well as speed. I as well as others maybe contemplating 16gb ram and wondering if its worth it.
    Reply
  • Chris383 - Monday, July 25, 2011 - link

    I think you guys are missing the point of faster memory. It just depends on the work load most applications are written for linear code or at least i am guessing so. But what happens when you add more than one program at the same time or 3-5 programs at the same time i think then you would start to see why memory performance really does matter. And some games not most but some games will start to show a very big increase in performance with faster memory. Example FarCry2, GTA4, Starcraft2, now some of this maybe caused by poor memory management of the video card or lack of vmem but from my findings even with enough vmem you still will see some very big changes in FPS with faster/tighter memory speeds (provided your not cpu or gpu limited)

    That being said for most people playing games at lower resolutions like 1080 and below memory speed is really not needed 1333 will suffice plenty good but when your doing 3,4+MP screens you will defiantly want to take into consideration some faster memory for your rig.
    Reply
  • ypsylon - Tuesday, July 26, 2011 - link

    I don't get it why home users are so over-excited about memory over 1600 MHz? For gaming buying e.g. 2133 memory is as wise as buying Mercedes Maybach for trips to local grocery store.

    Fast memory has very limited usage (medicine, NASA etc...) and certainly home desktop/gaming rig doesn't qualify for that. Furthermore if you want to OC system, then whole point of OC is to buy cheap [read: cheap doesn't = crap] and squeeze every little bit of performance out of it. Stay at 1333/1600 level. 2000 or more is for [beeep!] with humongous e-penis running benchmarks 365/24/7. Biggest advantage of 1333/1600 range is that by default pretty much every chipset and motherboard support it right now.

    Running perfectly standard Kingstons 1333 at 1800 without any fancy cooling or changed timings, just bumped BClk on my x58. Even with current prices I'm 100$+ up just by doing this (2 triple sets). And RAMDisk created on that memory certainly isn't slow and eats every SSD for breakfast.
    Reply
  • Hrel - Tuesday, July 26, 2011 - link

    SO happy you posted this. I JUST ordered a new laptop, didn't upgrade the RAM at all cause it was overpriced. Now I know I'm going to order 2 4GB DIMMS of DDR3 1600 for it, Cas latency 9 be damned, haha. Thanks so much!

    I was apparently giving way too much credit to CAS latency, I was going to get 1066 Cas 7. Didn't realize pure bandwidth was so important nowadays. I remember an old memory article like this comparing DDR3 for i7 920's and such, whatever that family is called. 1600 cas 7 came out on top their. Odd that Sandy Bridge changes that, but I'm glad I know.

    I'd like to see more articles like this, and less articles about EVERY stupid smartphone under the sun.
    Reply
  • Rick83 - Wednesday, July 27, 2011 - link

    7/1,066,000,000Hz = ~6.56 e-9 s
    9/1,600,000,000Hz = 5.625 e-9 s
    So in fact, the 1600Mhz CL9 RAM has a one nanosecond lower effective latency.

    Always remember that CAS latency is in cycles, which take a different amount of time according to the clock speed.
    Reply
  • schulmaster - Wednesday, July 27, 2011 - link

    Tests are not 'ran', tests are 'run.' You can say we ran tests, but you must say we have run them. This site is way to technically proficient and intelligent for glaring mistakes in homepage articles. I know for at least some of you, English is a second+ language; if that's the case, send me your articles and I'll proof them for free. Reply
  • Black1969ta - Wednesday, July 27, 2011 - link

    "This site is way to technically proficient"
    to here refers to excessive, like too much but you left out the extra "o" so the means something totally different.

    If you want to be a Grammar Nazi, use proper English, especially when you are using it as an advertisement.
    Reply
  • schulmaster - Thursday, July 28, 2011 - link

    my man. Reply

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