Results, Overclocking, and Conclusion
Test Setup and Initial Impressions
With memory prices at an all time low, I thought it would be interesting to pair 16GB of memory with one of the latest AMD A8-3850 processors. This is a Llano based quad core part running at 2.9 GHz and a full 400 stream unit Radeon GPU running at 600 MHz. AMD recently released their “K” series of parts which feature unlocked multipliers. I do not yet have access to one of these products, but I am pretty sure that overclocking the top end A8-3870 to 3.5 GHz core and 800 MHz GPU will show a marked increase in memory usage.
The motherboard used is the Asus F1 A75-V Pro. This is a slightly higher end model for the new AMD processors, but it is not of the EVO series that Asus is famous for. This still should be able to push the setup at a decent level; then again, we are talking about slightly upgraded Athlon II based cores and integrated graphics. The performance ceiling is set a bit low as it is.
16GB and a AMD A8-3850 do not seem like a logical pairing, but at a non-sale price of $129 why not?
When first installing these DIMMS on this particular motherboard, I ran into some instability. I only inserted two DIMMs out of the possible four, and still experienced instability at stock settings. I increased the voltage on the DIMMs to 1.6v, and the instability went away. Using four DIMMs will require a user to use 1.6v for stability with stock timings. This could be an issue with the motherboard or the actual CPU in this case.
With the A series processors from AMD, it is easy to see the advantages of using faster memory. In this case, I thought it is also good to use more DIMMS. AMD has long had a memory controller that seems to love higher DIMM counts. While overclocking with more DIMMS is not as good, using four at stock settings tends to give a couple extra percent of performance in memory limited applications. Officially AMD does not support four DIMMS at DDR-3 1866, but that does not necessarily mean that it will not work if a user is patient enough with settings.
Though streaming benchmarks do not show any uplift in performance, other benchmarks which utilize both the CPU and GPU did see about a 5% increase in overall performance. I did ask AMD why it appears as though adding extra DIMMS improves performance, and here is their response:
“I suspect there are a couple of reasons for the small uplift with 2 DIMMs/channel. Most of the memory benchmark programs look at memory-to-core throughput. Part of memory feeds the graphics engine and they probably do not account for that. With 2 DIMMs, the graphics memory may be stuck on top of memory wich puts it in the second pair of DIMMs while the memory benchmark may be running in the lower 8 GB space (first DIMM pair). Without the sharing, there will be less paging and less competition for the bottlenecked area. It’s not a 100% giveback as the same physical data wire are used, but overlap can happen there as well when one DIMM is doing a RAS cycle and the other DIMM pumps out data.”
We must also consider that this is a budget level CPU with integrated graphics running with 16 GB of memory. This is definitely overkill for most systems in this price range, and likely the extra memory is being put to good use by the CPU, GPU, and operating system. So with these things in hand I thought I would look at performance with 2 and 4 DIMMS at a variety of speeds. Let’s take a look at the results.
Well that isn’t how it was supposed to work. None of the expected uplift from using 4 DIMMs was evidenced. My guess here is that when all four DIMM slots are populated, the Asus board pulls back some of the lower level latencies to improve stability. During testing with four DIMMs I never had a crash over many hours of testing. But I also did not see any real boost in performance with this configuration.
These DIMMs were easily able to hit DDR-3 1950 speeds at slightly elevated voltages. Going full out at 1.65 would likely net DDR-3 2000 speeds with again relaxed timings. If a user only uses two of the four DIMMs, they will be able to go much higher than that, and I have seen results approaching DDR-3 2150 speeds with 10.11.10.30 timings at 1.65v.
Stability is decent while overclocked, but when using four DIMMs things just get constrained by the design of the memory controller in the processors. Most of these units were designed primarily around pushing one DIMM per channel, and when two DIMMs get used then timings often require being retarded to a certain degree to achieve stability. Again, it would be odd to pair this four DIMM kit with an AMD A series processor in the first place, but at the prices we are seeing for memory it is not all that great of a stretch.
If a user is planning on buying a new computer, it is nearly a no brainer to stock up on the fastest and largest memory kits available. While 16GB is a bit overkill for a Llano based processor, price is not necessarily a barrier for entry. Currently these DIMMS retail for around $129 US, and often there are rebates available that will take them down to $90. Consider that just over a year ago a user could get 2 x 2GB DDR-3 1600 kits for around that price. Now we have four times that memory density at a faster speed.
I have been testing these parts far longer than I should have been. They have been in constant use for the past six months and I have not had a single problem with them. Initial quality from GSkill appears good in this case. Now, that being said, there will always be DIMMs that will fail. I also do work for an engineering firm that buys quite a few computers. I have had GSkill DIMMs that have failed, but the RMA process is painless and fast. A user simply goes to their website, fills out an RMA form and emails it in, and within a day gets an RMA number back. Once the DIMMs are packed up and sent away, it takes about a week for replacement DIMMs to be delivered. It is not overnight service, but on several occasions where I have used the RMA process, it was relatively quick and entirely painless.
New and upcoming processors from AMD and Intel will utilize faster memory. With the historic low prices of these DIMMs, I find absolutely nothing wrong with the product that GSkill is offering. While memory certainly did hit a “generic” stage in terms of abilities and densities, we are entering a new golden age where these larger and more interesting kits will make a difference in everyday computing performance. The GSkill Ripjaw X 16GB DDR-1866 is an excellent choice for those looking to go in this direction.