Sandy Bridge Memory Scaling: Choosing the Best DDR3
by Jared Bell on July 25, 2011 1:55 AM ESTFinal Words
I think we confirmed what we pretty much knew all along: Sandy Bridge's improved memory controller has all but eliminated the need for extreme memory bandwidth, at least for this architecture. It's only when you get down to DDR3-1333 that you see a minor performance penalty. The sweet spot appears to be at DDR3-1600, where you will see a minor performance increase over DDR3-1333 with only a slight increase in cost. The performance increase gained by going up to DDR3-1866 or DDR3-2133 isn't nearly as pronounced.
As a corollary, we've seen that some applications do react differently to higher memory speeds than others. The compression and video encoding tests benefited the most from the increased memory bandwidth while the overall synthetic benchmark and 3D rendering test did not. If your primary concern is gaming, you’ll want to consider investing in more GPU power instead of a faster system memory; likewise, a faster CPU will be far more useful than more memory performance for most applications. Outside of chasing ORB chart placement, memory is one of the components least likely to play a significant role in performance.
We also found that memory bandwidth does scale with CPU clock speed; however, it still doesn't translate into any meaningful real-world performance. The sweet spot still appears to be DDR3-1600. All of the extra performance gained by overclocking almost certainly comes from the CPU overclock itself and not from the extra memory bandwidth.
Finally, although the effects of low latency memory can be seen in our bandwidth tests, they don't show any real world advantage over their higher latency (ahem, cheaper) counterparts. None of the real-world tests performed showed any reason to prefer low latency over raw speed.
Even though there's merely a $34 price difference between the fastest and slowest memory tested today, I still don't believe there's any value in the more expensive memory kits on the Sandy Bridge platform. Once you have enough bandwidth (DDR3-1600 at a small $9-$10 price premium), there's just not enough of a performance increase beyond that to justify the additional cost, even when it's only $34 between 4GB kits. Once you jump to the 8GB kits, the price difference for CL9 DDR3-1600 is a mere $8, but it becomes much more pronounced at $92 to move to DDR3-2133. We simply can’t justify such a price difference based on our testing.
Of course, testing with Sandy Bridge doesn't necessarily say anything about other platforms. It's possible that AMD's Llano and Bulldozer platforms will benefit more from higher bandwidth and/or better latency memory, but we'll save that article for another day. Also, we've shown that performance scaling on integrated graphics solutions can benefit, particularly higher performance IGPs like Llano. Ultimately, it's up to you to choose what's best for your particular situation, and we hope this article will help you make better-informed decisions.
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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?
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.xsilver - Friday, August 5, 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.
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.
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.
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.
Rick83 - Wednesday, July 27, 2011 - link
7/1,066,000,000Hz = ~6.56 e-9 s9/1,600,000,000Hz = 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.
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.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.
schulmaster - Thursday, July 28, 2011 - link
my man.