Memory? Why?

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Aaah memory.  It has been some time since we last had a memory review, and for good reason.  Memory got pretty boring.  Ten years ago this was not the case.  DDR was just fresh on the scene and we were starting to see memory speeds and bandwidths get to a place where it would have a significant effect on performance.  Latencies were of utmost importance, and the fastest DIMMs running at DDR 400 speeds were often quite expensive.  Then things sort of mellowed out.  DDR-2 did not exactly bring faster performance over DDR initially, and it was not until DDR-2 800 and 1066 speeds that we actually saw a significant boost over previous gen DDR 1.  DDR-3 brought even more yawns.  With the jump to integrated memory controllers from both AMD and Intel, DDR-3 speeds were nearly meaningless.

The primary reason for this rather vanilla time in the memory market was that of individual bandwidth needs for CPU cores.  Most research into this issue points to an individual CPU core needing only 3 to 4 GB/sec of bandwidth to support its data needs.  AMD and Intel have gone to great lengths to increase the efficiency of not only their memory controllers and prefetchers, but also the internal caches so fewer main memory accesses are needed.  So essentially a quad core processor would really only need upwards of 12 to 13 GB/sec of bandwidth in real world scenarios.  DDR-3 1333 memory modules in a dual channel configuration would be able to support that kind of bandwidth quite easily.  So what exactly was the point of having faster memory?  Also, CPUs using DDR-3 memory are not as sensitive to latencies as we have seen in previous generations of parts.

When we look at previous generations of chips such as the i7 900/800/700 series from Intel and the Phenom II/Athlon II products from AMD, none of them were being held back by memory.  The i7 900 series had a triple channel memory controller which could provide upwards of 26 GB/sec of streaming bandwidth by simply using DDR-3 1333 modules.  Even with six Hyperthreading cores hard at work, the memory bus was a non-issue when it came to performance.  Sure, a user could overclock the bus and get higher stream numbers, but real world applications would see little to no performance increases overall.  The Phenom IIs were even more lackadaisical when it came to memory speeds.  While the CPUs were able to support DDR-3 1600 speeds, there again was little to no overall performance increases with the faster memory when running the CPU at stock speeds.  If a user wanted to overclock the northbridge and memory controller portions of the CPU from 2.4 to 2.6 GHz, only then they would see a jump in performance when going to DDR-3 1600 speeds.

The memory world was boring.  Sure, we saw some interesting heat spreader designs, some modules that would go above DDR-3 2000 speeds, but overall the industry was wallowing in the doldrums.  Then a couple of interesting things happened.  The first was that we started to see the densities of these DIMMs double up.  Instead of the insanely common 2 x 2GB modules, we started to see relatively inexpensive 2 x 4GB parts hitting the market.  Next we started to see the prices on all DIMMs start to drop dramatically.  I thought it was a pretty big deal when the first 2 x 4GB DDR-3 1333 parts hit the market for around $175 US.  From that point on we started to see a gradual decline in prices as well as the gradual increase in memory speeds.

The next big thing was the introduction of the latest CPU architectures.  Intel’s Sandy Bridge parts increased the default memory speeds with motherboard manufacturers adding more to that number through overclocking measures.  JEDEC approved a DDR-3 1866 spec, which is well above that of the previous DDR-3 1600 that was so common.  AMD released their Llano based APUs which feature a totally redesigned memory controller and crossbar connection between the controller, GPU, and CPU portions.  AMD officially implements DDR-3 1866 with this CPU, and it is dearly needed when both the CPU and GPU really get going.  AMD also released the new Bulldozer architecture.  This chip again has a redesigned memory controller that supports up to DDR-3 1866, and the “8 core” architecture comprised of the four modules does require significantly more bandwidth than the previous Phenom II high end parts to keep the cores adequately fed with data.

4 DIMMS equaling 16GB of memory was once unheard of for the average user.  Only server level products (with server level prices) featured these densities.

So now we are off!  The CPU industry has just provided a new momentum for memory manufacturers to improve upon their offerings, and give us a good reason to again invest in higher end memory products.  GSkill was kind enough to provide a set of 4 x 4GB DDR-3 1866 DIMMS for testing and to see how much of an improvement in performance we expect to see with at least the AMD A8-3850 processor.

The GSkill Ripjaws X 16GB DDR-3 1866 Kit

GSkill likes red.  It is a color that represents energy and power.  The heatspreaders on these DIMMS are a nice shiny red with some pleasant looking decals.  The heatspreaders do a good job in keeping the DIMMS cool under both normal and overclocked situations.  The kit is comprised of four matched 4GB DIMMs.  Of course, “matched” is a bit of a misnomer.  While checked for compatibility, the vast majority of mass produced memory modules are going to exhibit the same electrical and speed properties of the module next to them in line.  So as long as these modules work and are based on the same PCB design and binned memory chips, then they are not going to have any issues when running in pairs and quads.

These particular modules run at the stated DDR-3 1866 speeds with timings at a nice and low 1.5 volts.  The DIMMS include the Intel XMP technology, which provide optimized low level timing information to motherboards which support this functionality.  Most Intel boards do support XMP, but Asus also includes this functionality in most of their latest AMD products.  Using the XMP profiles is key to wringing every ounce of performance out of these particular DIMMS, unless of course the user has a very detailed knowledge of how memory timings work and want to push these products to their limit.  XMP should also provide some extra leeway when overclocking these parts above 1866 levels by loosening up the timings and maintaining stability.

These modules are primarily aimed at the user wanting to run the latest i7 processors in quad channel mode.  But this does not exclude other systems that are dual channel based.  As long as a motherboard has four DIMM slots, these should work perfectly fine in systems powered by either Intel or AMD.

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