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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  • 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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