Sandy Bridge Memory Scaling: Choosing the Best DDR3
by Jared Bell on July 25, 2011 1:55 AM ESTMemory 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.
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.
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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Kevin G - Monday, July 25, 2011 - link
One thing worth noting is that the memory controller has to run at least twice the clock speed of the memory (ie, the memory controller runs at 3.2 Ghz for 1600 Mhz DDR3 rated memory). This is one of the reasons why Intel doesn't officially support memory speed higher than 1600 Mhz. Running the CPU cores and memory controller at the same clock speed should produce a benefit even if memory speed isn't improved (ie running the CPU and memory controller at 4.8 Ghz with 1600 Mhz memory). It would be interesting to see how just scaling the memory controller's speed affected performance.I wish that their were a few game tests utilizing the integrated GPU. For a desktop, using a discrete graphics card for gaming is a new brainer over Intel's integrated graphics. However many laptops will only use Intel's solution and thus improving memory performance could be a means of improving gaming performance here. Further more, laptops are often lower resolution than 1920 x 1080 and thus the performance delta between memory speeds would be wider.
RussianSensation - Monday, July 25, 2011 - link
But even if laptops run at lower resolutions, they have much weaker CPUs and GPUs and generally have slow 5400 rpm hard drives. So if anything, memory speed will be even less important in a laptop since a laptop will be faced with all kinds if I/O, GPU and CPU bottlenecks.Improving performance of Intel's gaming solution with faster memory is a waste of time. HD3000 is just a dog. If you want a budget gaming laptop, you get Llano. No amount of memory bandwidth is going to translate into a more playable gaming experience on the HD3000.
Kevin G - Monday, July 25, 2011 - link
Except that Llano is in the same situation as it too needs fast memory for better graphics performance. If DIMM manufacturers start rolling out high performance memory for Llano, Sandy bridge laptops can also benefit. So why not actually test to see what those benefits could be?orenlevy - Tuesday, July 26, 2011 - link
there is defenetly gpu improvment on hd3000 i dont know why you are not benching on Z68 platform. personally i have z68 htpc and sure i noticed different lateness on normal use. we always like sppedy windows poping and that simply whats happans.personally i say to myself "oh its about time to squeez little bit more from the sandybridge" even the G840 behave so different on 1600M cl8 Z68...
jabber - Monday, July 25, 2011 - link
As its such a waste of life. RAM hasnt been fun or that important since the good old DDR days.They may as well just hardwire 4GB of bog standard ram onto the motherboard for most folks.
silverblue - Monday, July 25, 2011 - link
Maybe they have, but RAM speed is important for iGPUs and especially so for APUs.For those wondering where the Llano equivalent is...
http://www.anandtech.com/show/4476/amd-a83850-revi...
silverblue - Monday, July 25, 2011 - link
Duh. The link is on the final page of this article.Kevin G - Monday, July 25, 2011 - link
The main reason why RAM still comes on DIMMs is due to reliability and the need for expansion. Cost is also a factor, especially for motherboards with lot of RAM soldered on to it.However, soldering down RAM in some situations does make sense. Expandability in laptops for example. Another area where soldiered RAM on a desktop motherboard would make sense is with the overclocking crowd. The RAM could be placed closer to the CPU socket which could easily increase clock speeds. The elimination of the edge connector on the DIMM would also significantly enhance signal strength too. Physical placement on the motherboard would allow for better cooling (larger heat sinks or water cooling with direct contract with the RAM chips). There would also be room for robust power delivery to the RAM chips on the motherboard.
dac7nco - Monday, July 25, 2011 - link
I' glad there are still RAM reviews; 1.5v DDR3 1600 / CAS 7/7/7 gets me an additional 1 to 2 FPS in long Handbrake transcodes, which is a big part of my bread and butter.Keep in mind, 1.5v, no higher, is the DDR3 spec, which is why you'll never see ECC DDR3 registered memory rated above that. Keep this in mind, Anand: Control your people! X58-rated memory has no place today.
Daimon
jabber - Monday, July 25, 2011 - link
I still think the main selling pint for RAM is - How well does it match my motherboard?Maybe a round up of modules with fancy spreaders and how they look in Asus/Gigabyte/Asrock/MSI boards.