Memory Scaling on Haswell CPU, IGP and dGPU: DDR3-1333 to DDR3-3000 Tested with G.Skill
by Ian Cutress on September 26, 2013 4:00 PM ESTFor our single discrete GPU testing, rather than the 7970s which normally adorn my test beds (and were being used for other testing), I plumped for one of the HD 6950 cards I have. This ASUS DirectCU II card I purchased pre-flashed to 6970 specifications, giving a little more oomph. Typically discrete GPU options are not often cited as growth areas of memory testing, however we will let the results speak for themselves.
Dirt 3: Average FPS
Dirt 3 commonly benefits from boosts in both CPU and GPU power, showing near-perfect scaling in multi-GPU configurations. When using our HD6950 however there seems to be little difference between memory settings with no trend.
Dirt 3: Minimum FPS
Minimum frame rates show a different story – Dirt 3 seems to prefer setups with a lower CL – MHz does not seem to have any effect.
Bioshock Infinite: Average FPS
Single GPU frame rates for Bioshock has no direct effect for memory changes with less than 2% covering our range of tests.
Bioshock Infinite: Minimum FPS
One big sink in frame rates seems to be for 1333 C7, although given that C8 and C9 do not have this effect, I would presume that this is more a statistical outlier than an obvious trend.
Tomb Raider: Average FPS
Again, we see no obvious trend in average frame rates for a discrete GPU.
Tomb Raider: Minimum FPS
While minimum frame rates for Tomb Raider seem to have a peak (1600 C8) and a sink (2400 C12), this looks to be an exception rather than the norm, with minimum frame rates typically showing 35.8 – 36.0 FPS.
Sleeping Dogs: Average FPS
Frame rates for Sleeping Dogs vary between 49.3 FPS and 49.6 FPS, showing no distinct improvement for certain memory timings.
Sleeping Dogs: Minimum FPS
The final discrete GPU test shows a small 5% difference from 1600 C11 to 2400 C11, although other kits perform roughly in the middle.
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Rob94hawk - Friday, September 27, 2013 - link
Avoid DDR3 1600 and spend more for that 1 extra fps? No thanks. I'll stick with my DDR3 1600 @ 9-9-9-24 and I'll keep my Haswell overclocked at 4.7 Ghz which is giving me more fps.Wwhat - Friday, September 27, 2013 - link
I have RAM that has an XMP profile, but I did NOT enable it in the BIOS, reason being that it will run faster but it jumps to 2T, and ups to 1.65v from the default 1.5v, apart from the other latencies going up of course.Now 2T is known to not be a great plan if you can avoid it.
So instead I simply tweak the settings to my own needs, because unlike this article's suggestion you can, and overclockers will, do it manually instead of only having the options SPD or XMP..
The difference is that you need to do some testing to see what is stable, which can be quite different from the advised values in the settings chip.
So it's silly to ridicule people for not being some uninformed type with no idea except allowing the SPD/XMP to tell them what to do.
Hrel - Friday, September 27, 2013 - link
Not done yet, but so far it seems 1866 CL 9 is the sweet spot for bang/buck.I'd also like to add that I absolutely LOVE that you guys do this kind of in depth analyses. Remember when, one of you, did the PSU review? Actually going over how much the motherboard pulled at idle and load, same for memory on a per DIMM basis. CPU, everything, hdd, add in cards. I still have the specs saved for reference. That info is getting pretty old though, things have changed quite a bit since back then; when the northbridge was still on the motherboard :P
Hint Hint ;)
repoman27 - Friday, September 27, 2013 - link
Ian, any chance you could post the sub-timings you ended up using for each of the tested speeds?If you're looking at mostly sequential workloads, then CL is indicative of overall latency, but once the workloads become more random / less sequential, tRCD and tRP start to play a much larger role. If what you list as 2933 CL12 is using 12-14-14, then page-empty or page-miss accesses are going to look a lot more like CL13 or CL14 in terms of actual ns spent servicing the requests.
Also, was CMD consistent throughout the tests, or are some timings using 1T and others 2T?
There's a lot of good data in this article, but I constantly struggle with seeing the correlation between real world performance, memory bandwidth, and memory latency. I get the feeling that most scenarios are not bound by bandwidth alone, and that reducing the latency and improving the consistency of random accesses pays bigger dividends once you're above a certain bandwidth threshold. I also made the following chart, somewhat along the lines of those in the article, in order to better visualize what the various CAS latencies look like at different frequencies: http://i.imgur.com/lPveITx.png Of course real world tests don't follow the simple curves of my chart because the latency penalties of various types of accesses are not dictated solely by CL, and enthusiast memory kits are rarely set to timings such as n-n-n-3*n-1T where the latency would scale more consistently.
Wwhat - Sunday, September 29, 2013 - link
Good comment I must say, and interesting chart.Peroxyde - Friday, September 27, 2013 - link
"#2 Number of sticks of memory"Can you please clarify? What should be that number? The highest possible? For example, to get 16GB, what is the best sticks combination to recommend? Thanks for any help.
erple2 - Sunday, September 29, 2013 - link
I think that if you have a dual channel memory controller and have a single dimm, then you should fill up the controller with a second memory chip first.malphadour - Sunday, September 29, 2013 - link
Peroxyde, Haswell uses a dual channel controller, so in theory (and in some benchmarks I have seen) 2 sticks of 8gb ram would give the same performance as 4 sticks of 4gb ram. So go with the 2 sticks as this allows you to fit more ram in the future should you want to without having to throw away old sticks. You could also get 1 16gb stick of ram, and benchmarks I have seen suggest that there is only about a 5% decrease in performance, though for the tiny saving in cost you might as well go dual channel.lemonadesoda - Saturday, September 28, 2013 - link
I'm reading the benchmarks. And what I see is that in 99% of tests the gains are technical and only measurable to the third significant digit. That means they make no practical noticeable difference. The money is better spent on a difference part of the system.faster - Saturday, September 28, 2013 - link
This is a great article. This is valuable, useful, and practical information for the system builders on this site. Thank you!