by Ilya Gavrichenkov
05/04/2007 | 09:53 PM
Even if you are not really following the news from the memory market on a regular basis, you may have definitely noticed that the working frequencies of the DDR2 memory modules have actually grown pretty modestly over the past year. In the end of last summer we tested DDR2-1100 memory modules from Corsair and OCZ (for details see our article called DDR2 SDRAM to Hit 1.1GHz: Corsair Dominator vs. OCZ PC2-8800 Gold Edition). After the launch of these memory modules the manufacturers of DDR2 memory for computer enthusiasts couldn’t really offer anything principally new for quite some time. It is only recently that we started witnessing some minor movement towards higher memory speeds: Corsair Company managed to shift the top speed limit to 1250MHz, and OCZ Technologies – to 1200MHz. These relatively small increases from the overclocker memory makers are not incidental. There are two reasons for that.
First, until recently it didn’t really make much sense to manufacture faster memory. Even advanced users and extreme overclockers didn’t really require ultra high-speed DDR2 SDRAM. Widespread Intel core logic sets for Core 2 Duo processors could only take real advantage of the 1200MHz+ memory with an extremely successfully overclocked processor in the system. Moreover, the performance improvement obtained thanks to this high-speed memory was ephemeral, and analogous performance level could be achieved with DDR2-800 SDRAM running with aggressive timing settings (for details see our article called Choosing the Right Memory for Core 2 Duo Platform - Part 1). As for the systems built around AMD Athlon 64 processors, we can skip them here, because they are no longer of interest to the majority of computer enthusiasts and hardcore gamers. In other words, high-frequency memory kits could become really demanded by the market when the next-generation chipsets got popular.
Secondly, design and manufacturing of high-frequency DDR2 memory has been and still is being slowed down by the absence of necessary memory chips with sufficient frequency potential. The makers of DDR2 SDRAM chips haven’t yet offered anything better than the renowned Micron D9GMH chips that are still the best components for overclocker memory modules available in the market these days. So, further production of faster DDR2 SDRAM memory modules requires even more thorough selection of components and hence increases the labor-intensiveness and production cost of the end product.
Everything I have just said means that there should have been a very good reason for the manufacturers to start making 1200MHz DDR2 memory. And this reason is the Nvidia nForce 680i SLI based mainboards that started invading the market and have already become pretty popular (for details see our article called Nvidia nForce 680i SLI Chipset Review). The thing is that DDR2-1200 SLI-Ready Memory support is one of the official characteristics of this chipset. Moreover, nForce 680i SLI allows pseudo-synchronous clocking of the memory bus, which enabled DDR2 SDRAM overclocking independently of the set FSB frequency. These peculiarities shaped up the demand for high-speed memory modules: this demand was created by dedicated computer enthusiasts eager to fight for higher performance of their systems at any rate.
Today we are going to introduce to you three 2GB kits of dual-channel DDR2 SDRAM that offered by the two leaders of the memory market for advanced users – Corsair and OCZ. We will discuss solutions designed to work at 1150MHz and 1250MHz default frequencies and will try to find out how the actual users can benefit from this endless hunt for higher memory speeds. Especially since the same Nvidia nForce 680i SLI chipset also offers an alternative approach to selecting the most optimal DDR2 SDRAM modules based on latency minimization and for that purpose offers efficient tools for 1T Command Rate adjustment.
Like all high-speed overclockers memory modules, the Corsair solution designed to work at 1150MHz belongs to the Dominator series. We have already reviewed some products from the same family in our article called DDR2 SDRAM to Hit 1.1GHz: Corsair Dominator vs. OCZ PC2-8800 Gold Edition, so we know that the major distinguishing feature of Corsair Dominator memory modules is their original cooling system.
Each memory module from this series is equipped with aluminum heat-spreaders 51mm tall with not very deep ribbing on the front side and comb-shaped top edge. These heats-spreaders feature much greater surface area than the traditional stamped plate heat-spreaders, therefore they ensure efficient heat dissipation from the memory chips working at much higher voltage than the common 1.8V. Moreover, Dominator modules use special PCB with an additional pair of comb-shaped heat-spreaders fastened to its upper side. Corsair engineers introduced this solution to provide proper dissipation of the heat that the BGA memory chips transfer to the PCB through contact surfaces. This way each Dominator memory module features four heat-spreaders at the same time: Corsair calls this feature DHX (Dual Heat Exchange).
The Corsair Dominator TWIN2X2048-9136C5D kit that we are look at today contains two identical Corsair CM2X1024-9136C5D memory modules, each with 1GB capacity. The kit is intended to work in dual-channel mode at 1142MHz with 5-5-5-15 timing settings (at 2T Command Rate). The default voltage for this memory module kit is 2.1V.
Corsair specifically points out that all their memory modules have been tested in an Nvidia nForce 680i SLI based reference mainboard from eVGA. So, Corsair Dominator TWIN2X2048-9136C5D shouldn’t experience any operational problems with similar mainboards from BFG, XFX, ECS and Biostar. I would like to draw your attention to this fact specifically, because the mainboards built around nForce 680i SLI chipset but featuring non-reference design may not support this memory at its default frequencies. For example, Asus Striker Extreme and abit IN9 32X-MAX Wi-Fi mainboards that we have recently written about couldn’t work stably with the memory running at speeds beyond 1100MHz. therefore, you should pay special attention to compatibility matters when buying Corsair Dominator TWIN2X2048-9136C5D memory. At this time we can confirm that this DDR2 SDRAM kit is fully compatible only with standard (reference) mainboards on Nvidia nForce 680i SLI and Asus P5B Premium.
Each of the memory modules from the Corsair Dominator TWIN2X2048-9136C5D kit features its own sticker with the product part number, working frequency, capacity and timings. The marking reads no information on the voltage.
The SPD of these memory modules contains the parameters that ensure the best compatibility. The actual working frequencies, timings and voltages are provided in the EPP (Enhanced Performance Profile) used exclusively by Nvidia chipsets. Note that the screenshot reads memory module frequency as 1100MHz. It is a mistake in the Everest 4.00.976 utility. If the EPP is activated, the BIOS Setup detects the claimed 1142MHz frequency alongside with all default timings without any problems.
In conclusion I would like to say that Corsair Dominator TWIN2X2048-9136C5D is built using hand-picked Micron D9GMH (B6-3) chips.
Besides Dominator TWIN2X2048-9136C5D, Corsair is also offering even faster memory modules designed to run at 1250MHz frequency. They also belong to the Dominator family and are called Corsair Dominator TWIN2X2048-10000C5DF. I would like to stress that it is the today’s fastest mass DDR2 SDRAM for overclockers.
The design of Corsair Dominator TWIN2X2048-10000C5DF memory modules is identical to any other solution from the Dominator family. They are designed with DHX technology and are equipped with top-of-the-line comb-shaped heat-spreaders typical of the entire line-up – four per module. However, the fastest Dominator memory modules come with a more advanced accessories bundle: the two identical CM2X1024-10000C5D modules are accompanied with a specially designed Dominator Airflow Fan.
This cooler is fastened to the DIMM slot clips and directs airflow to the memory modules installed in them preventing them from overheating. From the design standpoint, Dominator Airflow Fan consists of three 40-mm fans with a little over 5,000rpm rotation speed installed into a single frame. All three fans blow the air directly to the memory modules, which generates a pretty impressive airflow in the corresponding area. Unfortunately, despite the indisputable efficiency of this cooling solution, it turns out quite noisy, which slightly spoils the overall impression.
Corsair Dominator TWIN2X2048-10000C5DF memory modules most likely require an additional cooler because of significant increase in the operational voltage in nominal mode. Dominator TWIN2X2048-10000C5DF memory modules owe their ability to run at 1250MHz frequency and 5-5-5-18 timings (at 2T Command Rate) to the increased voltage that by default is set at 2.4V.
Although the manufacturer has legalized this high memory voltage in the official specifications, I dare express some concerns regarding the safety of the modules at such voltage. Nvidia is also talking about possible outcomes of such extreme working conditions. According to Nvidia engineers, long-term operation of DDR2 SDRAM at such high voltage may ruin semiconductor chips structure and thus put the memory modules out of service. The only consolation in this case is the fact that Corsair provides lifetime warranty on all their memory modules.
Before shipping them to the stores, Corsair tests all Dominator TWIN2X2048-10000C5DF memory kits in nominal mode on eVGA 122-CK-NF67-A1 mainboards. So, they can actually guarantee proper compatibility only with nForce 680i SLI based mainboards designed by Nvidia.
The stickers you can see on each of the memory modules from the Corsair DDR2-1250 SDRAM kit contain typical info: part number, frequency, timings and capacity.
The SPD of these memory modules reports traditional info to ensure that they will work in any mainboard with default settings. As for the actual parameter values, they are located in the corresponding EPP profile. Everything meets the spec here (Everest 4.00.976 utility is again 50MHz off), so if you activate the EPP technology in the BIOS Setup, the memory subsystem will get configured automatically.
I would like to point out that the difference in default working frequencies between Corsair Dominator TWIN2X2048-10000C5DF and Corsair Dominator TWIN2X2048-9136C5D can be explained not only by higher voltage. These modules use slightly different electronic components. Faster Dominator uses modified Micron chips with lower access time - D9GMH (B6-25E). This is exactly why Corsair Dominator TWIN2X2048-9136C5D modules cannot be turned into higher-performing and more expensive Dominator TWIN2X2048-10000C5DF by just raising the voltage and adding active cooling solution.
Although the today’s fastest DDr2 memory from OCZ runs at 1200MHz, at the time of testing we only had a slightly slower kit working at 1150MHz, however the results for the 1200MHz kit will follow shortly, so stay tuned. Nevertheless, the kit featured in this article, OCZ DDR2 PC2-9200 FlexXLC Edition, boasts a very worthy set of interesting features, too. The main one is certainly the fact that it belongs to the FlexXLC family.
The memory from OCZ FlexXLC (Xtreme Liquid Convention) series, just like Corsair Dominator, is remarkable for the cooling system designed for it. To dissipate the heat from the DDR2 memory chips OCZ uses massive heat-spreaders built from aluminum and copper parts. Being 64mm tall, featuring comb-shaped upper edge and copper plates pressed directly to the memory chips, FlexXLC system ensures very efficient cooling. However, the key feature of these heat-spreaders is definitely their ability to get connected to a liquid-cooling system. Therefore, there is through-duct in the upper aluminum part of the heat-spreaders that exits via two connecting pipes that can host thin tubes with a quarter inch inner diameter.
Note that although OCZ FlexXLC memory modules can be used with liquid cooling, the manufacturer doesn’t insist on it. This memory can also work just fine without it, the heat-spreaders surface area is large enough to ensure proper efficiency in systems with traditional air cooling.
OCZ DDR2 PC2-9200 FlexXLC Edition memory kit consists of two 1GB modules that are intended for operation in dual-channel mode at 1150MHz frequency, with 5-5-5-18 timings (at 2T Command Rate) and 2.3V voltage. Moreover, the manufacturer guarantees that the modules will also remain operational even at higher 2.35V voltage during overclocking.
Each of the OCZ DDR2 PC2-9200 FlexXLC Edition memory modules carries a sticker with the product part number, memory speed, default timings and capacity of each.
The modules SPD as usual reads the info ensuring best compatibility with the existing platforms. The actual working parameters of OCZ DDR2 PC2-9200 FlexXLC Edition and their values are written into the EPP profile, although the voltage is stated lower by mistake (again, the data reported by Everest 4.00.976 utility is 50MHz off, in BIOS Setup the frequency is detected correctly).
You may have noticed that there is a lot in common between OCZ DDR2 PC2-9200 FlexXLC Edition and above described Corsair Dominator TWIN2X2048-9136C5D, and it is not only the work modes that are similar. Both memory kits use the same Micron D9GMH (B6-3) memory chips.
Before we move on to the actual benchmark results of our today’s DDR2 SDRAM kits, let’s sum up all the nominal specifications of our today’s testing participants side by side:
OCZ DDR2 PC2-9200
2 x 1GB
2 x 1GB
2 x 1GB
Now that we have discussed the default specifications of the high-speed and at the same time pretty expensive memory kits, we get very curious to find out how well they can do during overclocking. For our overclocking experiments I put together a testbed with an overclocked Intel Core 2 Extreme processor and eVGA 122-CK-NF67-A1 mainboard (Designed by Nvidia) based on the most suitable for DDR2 SDRAM overclocking Nvidia nForce 680i SLI core logic set. So, our test platform looked as follows:
Since Nvidia nForce 680i SLI chipset allows pseudo-synchronous memory clocking, the FSB frequency remained unchanged during our memory overclocking experiments. To ensure the system was running stably during DDR2 SDRAM overclocking, we used Memtest86, S&M and SP2004/ORTHOS utilities.
First of all I decided to find the maximum frequencies for the most widely spread timing sets when the memory modules can work stably and reliably. All the memory kits were tested at their nominal voltage. The first batch of tests was run with Command Rate set to 2T. This allows the memory modules to hit higher working frequencies on the one hand and to project the obtained results to systems on Intel P965 chipset, where Command Rate parameter is locked strictly at 2T and cannot be changed.
So, you can see the maximum frequencies for each set of timings on the chart below. These are the frequencies when the memory remained stable and reliable.
With “easy’ timings of 5-5-5-15, which are practically nominal for all the modules participating, the best results belong to Corsair Dominator TWIN2X2048-10000C5DF, which managed to overclock to 1257MHz. This result is quite logical, because this memory is designed for the highest frequency, even according to the specifications. OCZ DDR2 PC2-9200 FlexXLC Edition and Corsair Dominator TWIN2X2048-9136C5D memory modules hit the same frequency of 1155MHz, which is also not surprising at all, as they both use identical chips. I would like to stress that these results indicate unambiguously that all high-speed memory modules are running almost at the utmost of their potential. They are very uneager to overclock beyond the specified frequencies. This once again proves that the frequency potential of the DDR2 SDRAM chips has been fully exhausted.
You can push the frequency a little bit higher, at least on DDR2-1150 SDRAM modules, by raising the voltage. For example, if you set the voltage of Corsair Dominator TWIN2X2048-9136C5D modules to 2.3V, you can push their frequency to 1164MHz with 5-5-5-15 timings and without losing operational stability. You can achieve the same with OCZ DDR2 PC2-9200 FlexXLC Edition, however in this case you will have to raise the voltage to 2.35V and use liquid-cooling for better heat dissipation.
By the way, since we came to speak about the option of using liquid-cooling systems with OCZ DDR2 PC2-9200 FlexXLC Edition memory modules. I have to say that the use of liquid-cooling solution hardly improves the overclocking potential of these modules. Although I have to admit that the operational temperature in this case gets considerably lower.
As for the opportunity to use the tested solutions with more aggressive timings, Corsair Dominator TWIN2X2048-10000C5DF continues to break all overclocking records here. The especially impressive result can be obtained with timing set to 4-4-4-12, as the memory in this case can run at frequencies up to 1143MHz. The memory modules on Micron D9GMH (B6-3) chips can hardly reach 1GHz frequency with the same timing setting.
We have every right to say the same about our testing participants running with 3-3-3-10 timings. Only the fastest Corsair Dominator TWIN2X2048-10000C5DF can overcome the psychologically important frequency level of 800MHz.
Besides the tests with 2T Command rate, we would also like to see the results with Command rate set to 1T. In this case the memory subsystem latency gets significantly lower. However, the test session demonstrated that the overclocking potential of DDR2 SDRAM drops dramatically with Command Rate set to 1T.
From the peak frequency standpoint, OCZ DDR2 PC2-9200 FlexXLC Edition appears the leader with 1T Command Rate setting. Corsair Dominator TWIN2X2048-9136C5D can also boast good functionality at 800MHz with 4-4-4-12 timings. However the DDR2-1250 Corsair Dominator TWIN2X2048-10000C5DF kit that was ahead of the others in the test session with 2T Command Rate, could only work stably at 800MHz with the timings set to 5-5-5-15.
However, you shouldn’t forget that using high-frequency memory with 1T Command Rate setting actually contradicts the mere idea of the high-speed memory: its ability to hit ultra high frequencies. You should keep in mind that overclocker memory manufacturers usually offer other specialized solutions intended to work with lower latencies.
Besides the practical study of the memory modules overclocking potential with different settings, I couldn’t help paying special attention to checking out their performance. It is extremely interesting to see how big of a performance boost will the system get if the memory is running at 1150MHz or 1250MHz. It is evident that the bandwidth of this memory subsystem is much higher than the processor bus bandwidth. Therefore, the question is: how justified is the intention of the overclocker memory makers to continue pushing up the working frequencies of their solutions? Especially, since lowering the latencies may eventually be a more efficient way of boosting the performance than raising the frequencies.
In order to check the efficiency of high-frequency memory I compared the performance of systems using DDR2-1150 and DDR-1250 SDRAM against the performance of systems equipped with DDR2-800 and DDR2-1067 with common timing settings. Note that among the results are the numbers obtained from memory modules with extremely low latencies. I am talking about DDR2-800 SDRAM running with 3-4-3-6-1T timings. Although the overclocker memory module makers do not officially ship solutions like that to the market, high-quality memory using Micron chips can sometimes work with these aggressive latencies. For example, for our today’s tests in this work mode I took Corsair Dominator TWIN2X2048-8888C4DF kit.
The first round of tests was performed in a system with 266MHz nominal FSB frequency. The testbed was absolutely identical to the one I have already described above. The only difference was the Core 2 Extreme X6800 CPU that was running at 3.2GHz frequency obtained as 12 x 266MHz.
First of all take a look at the practical bandwidth and memory subsystem latency measurements obtained with Everest utility:
The numbers are quite illustrative. The measures bandwidth of the bus between the processor and the memory reaches its maximum with DDR2-800 SDRAM with aggressive timings. Strange as it might seem, but the high-speed DDR2-1150 and DDR2-1250 loses here. So, it turns out that the bandwidth of the dual-channel DDR2-800 SDRAM is quite sufficient for efficient data exchange with the processor along the system bus working in nominal mode. In fact, this is quite logical. The bandwidth of the Quad Pumped processor bus working at 1067MHz is 8.5GB/s, while dual-channel DDR2-800 SDRAM should theoretically be able to transfer data at 12.8GB/s.
However, if we measure the latency of the memory subsystem, both DDR2-1150 and DDR2-1250 SDRAM, show better results than DDR2-800 memory with aggressive timings. From the practical latency standpoint, DDR2-800 with 3-4-3-6-1T timings loses to DDR2-1067 with 4-4-3-11-2T timings. It makes us question the undisputed efficiency of the DDR2-800 SDRAM with low timings, and hence we simply cannot make any conclusions without running some tests in real applications.
As we see, the situation in benchmarks aimed at revealing the performance of the entire system as a whole is somewhat different from what we have just seen in synthetic Everest tests. High-speed memory working at 1150MHz and 1250MHz allows gaining some noticeable performance advantage.
In games the picture is slightly different. We can’t claim that high-frequency memory modules are indisputable leaders here. And if DDR2-1250 SDRAM almost always outperforms the memory with low latencies, then DDR2-1150 SDRAM performs overall slower than DDR2-800 with 3-4-3-6-1T timings. At the same time, DDR2-1067 with 4-4-3-11-2T timings actually looks pretty good, demonstrating results close to ideal.
The application tests also prove that DDR2 memory working at 1250MHz provides unprecedented performance. As for DDR2-1150, it is again often behind DDR2-1067 as well as DDR2-800 with low latency.
The results we discussed above were obtained with the processor bus of our test platform configured in nominal 266MHz mode. However, expensive high-frequency memory kits are often purchased by enthusiasts and hence they are often used in systems with overclocked processor and overclocked system bus. That is why we decided to add another set of tests to our article. These tests were conducted with FSB working at 400MHz. In other words, the next set of benchmarks was performed with Core 2 Extreme X6800 processor working at 3.2GHz speed obtained as 8 x 400MHz.
At first come the results of synthetic benchmarks and Everest:
By increasing the system bus frequency to 400MHz we managed to raise its peak bandwidth to 12.8GB/s. And in this case the use of high-speed memory is theoretically much more justified. The results of our memory subsystem bandwidth measurements differ from those obtained with 266MHz FSB. Besides the general bandwidths increase we can also point out that high-frequency memory is now performing much better against the background of the low latency solutions. This gives us some hope that it will prove more efficient in real applications than in the previous test session.
The results of the popular SuperPi benchmark are not that much different this time. High-speed memory performs neck and neck with low latency memory.
Higher FSB frequency didn’t change the situation in games, either. Although DDR2-1250 ensures that we get maximum performance in almost all games, DDR2-1150 is not performing with the same confidence. We can only say that by using 1150MHz memory with 5-5-5-15 timings we can get the same level of system performance as with DDR2-1067 memory with 4-4-3-11-2T timings or DDR2-800 with 3-4-3-6-1T timings.
The results of application benchmarks are also not so promising. As you see, memory running at 1150MHz+ doesn’t let us get any higher result than with low latency DDR2-800. Only the flagship DDR2-1250 SDRAM retains the leadership here leaving the competitors behind in two benchmarks out of three.
The obtained results drive us to some pretty distressing conclusions about the prospects of ultra high-speed memory solutions working at 1150MHz and 1250MHz. As we have just seen in the tests, the Nvidia nForce 680i SLI chipset so beloved by overclocking fans allows attaining excellent performance levels even with slower DDR2 SDRAM. In particular, the opportunity to set Command Rate to 1T allows lower-speed DDR2-800 memory with aggressive 3-4-3-6-1T timings to perform as fast as DDR2-1150 SDRAM and sometimes even outperform the latter. DDR2-1067 also has settings that allow it to achieve similar level of performance: 4-4-3-11-2T. So, the only indisputable performance leader appears to be unique Corsair Dominator TWIN2X2048-10000C5DF modules that can operate at 1250MHz, although we will have to disregard their price point in this case.
However, it is important to understand that DDR2-800 with 3-4-3-6-1T timings or DDR2-1067 with 4-4-3-11-2T timings praised as an alternative to high-speed memory we are testing today is not a widely available product that you can get in any computer store for an affordable price. There are very few selected memory makers who offer overclocker modules like that. And moreover – what a surprise! – all this memory is built using the same remarkable Micron chips manufactured with 80nm process.
If we compare the memory modules we reviewed today with the more or less widespread mainstream solutions, then we will have to conclude that high-speed products provide 3-5% higher performance in real applications.
So, it turns out that the study of “high bandwidth vs. low latency” doesn’t give any clue regarding the most promising approach to increasing the performance. Increasing the memory working frequency as well as reducing the latencies may provide pretty similar performance boost. Moreover, the Corsair and OCZ memory modules we have discussed and tested today proved to feature certain “universality” reserve. They can not only work at extremely high frequencies, but can also function in high-performance work modes with low latencies.
High-speed memory modules from Corsair and OCZ that we have discussed today are remarkable achievements of the companies’ RND and engineering teams. To hit breakneck speeds that are still unattainable for solutions from other manufacturers of overclocker memory, Corsair Company developed special heat-spreaders with original design, while OCZ Technologies focused on the option to use liquid-cooling solutions on their memory. We can consider the efforts of both companies extreme success: the Corsair Dominator TWIN2X2048-9136C5D, OCZ DDR2 PC2-9200 FlexXLC Edition and Corsair Dominator TWIN2X2048-10000C5DF memory kits tested today work stably at 1150MHz and 1250MHz frequencies respectively with 5-5-5-15 timings. At the same time, these memory modules can also function with aggressive timing settings that may sometimes ensure even higher system performance.
In other words, an overclocker who decides to purchase any of these memory kits will undoubtedly be able to find the most optimal work mode for his/her specific needs. And this is one of the major advantages of expensive high-speed memory kits like that: with this memory in your system, you shouldn’t have any issue with overclocking or system optimization for maximum performance. Memory like that will ensure maximum level of performance in almost any configuration.
Considering good results obtained during our overclocking experiments and performance tests we decided to award the following two kits of overclocker DDR2 SDRAM with our prestigious Editor’s Choice award: