by Ilya Gavrichenkov
09/15/2006 | 10:08 AM
In our previous review of DDR2 SDRAM we took a look at memory modules capable of working at frequencies of 1GHz and even higher, yet those were not the fastest modules available. The tough competition between the leading manufacturers of fast, overclocker-friendly memory results in even better products. And since the manufacturers of DDR2 SDRAM chips memory modules are made from cannot yet offer any dramatic improvements in terms of frequency potential, the makers of advanced modules have to resort to various tricks to clock them at ever higher frequencies.
It was at the end of the last summer that Corsair and OCZ, the two leaders of the memory market, announced their new and faster-than-before modules that lifted the frequency bar from 1066MHz to 1100MHz. So, PC2-8000 and PC2-8600 modules were followed by PC2-8800. Their speed isn’t far better than that of the earlier products, but even this small performance growth should be regarded with interest considering the lack of a new raw material for fast memory (we mean DDR2 SDRAM chips that would have better overclockability than today). So, this review is all about the new products from Corsair and OCZ as they provoke just enough of questions to be discussed in a single article. Before talking about each of them individually, we’d like to single out the general principle behind the ultra-fast PC2-8800 DDR2 SDRAM.
There is no magic, actually. The manufacturers of fast overclocker-targeted memory work along three directions. First, they cull chips with greatest overclockability. Second, they develop a proper design of the memory module’s PCB because the wiring affects overclockability, too. Third, they increase voltage on the chips, which is the most efficacious method of increasing a module’s frequency potential. Increased voltage leads to higher heat dissipation, so additional measures should be taken to ensure proper cooling of the memory chips lest their lifecycle should prove too short. For example, DDR2 SDRAM modules rated for a 1GHz frequency usually have a voltage of 2.2-2.3V, which is 20-35% above the normal voltage of that memory type. Corsair and OCZ went further with their 1.1GHz products and increased voltage to 2.4V. Coupled with a painstaking selection of chips, this gave birth to DDR2-1100 SDRAM.
Corsair’s new memory is quite an innovative solution that comes under the unique marketing name of Dominator. Corsair’s approach to developing memory that would break all frequency records was creative: TWIN2X2048-8888C4DF modules don’t have analogs among Corsair’s earlier products and feature a bunch of innovative technologies and solutions.
Besides the engineers, Corsair’s marketing department has also taken part in designing the TWIN2X2048-8888C4DF as it is. In order to be able to write “the fastest memory” in the press-release, the new modules from Corsair were put into PC2-8888 rather than the PC2-8800 category, so their official frequency is 1111MHz rather than 1.1GHz. This 11MHz difference, so important from a marketing standpoint, doesn’t matter much to us end-users, so let’s take a look at the Dominator series TWIN2X2048-8888C4DF modules from a technical standpoint.
Each kit includes two 1GB DDR2 DIMMs. The kit specification promises that the modules are stable at 1111MHz with 4-4-4-12 timings (at 2T Command Rate) and a voltage of 2.4V. The manufacturer also claims the voltage can be increased to 2.5V without any risk for the modules.
Corsair didn’t limit itself to just setting the voltage higher. One glance over the TWIN2X2048-8888C4DF is enough to realize that this kit differs completely from its own predecessors as well as from competing products. The heat-spreaders on these sticks are larger than ordinary heat-spreaders installed on DDR2 SDRAM modules. The height of Corsair Dominator modules is 51mm, which is 20mm higher than the standard DIMM for overclocked systems and 6mm higher than Corsair Pro series modules. Moreover, the heat-spreaders on the TWIN2X2048-8888C4DF have some ribbing for better heat dissipation. As a result, these heat-spreaders, even though made of aluminum rather than copper, are good enough to cool memory chips that work at a 33% higher voltage than the normal voltage of DDR2 SDRAM chips. Well, the heat-spreaders on both sides of each Corsair Dominator module are only half the cooling system implemented in it. Corsair’s Dual-path Heat Exchange technology implies yet another way for heat dissipation. The technology is based on the assumption that about half the amount of heat generated by the memory chips goes into the module’s PCB, especially since the BGA packaging of DDR2 SDRAM chips (the contacts are located on the reverse side of the chip) provides an easy way for heat to go – right through the contacts. Considering this, Corsair’s engineers thought it proper to equip not only the chips, but the PCB as well, with heat-spreaders.
This is how it’s implemented: the PCB wiring of the Corsair TWIN2X2048-8888C4DF modules is basically the same as that of other company’s product, TWIN2X2048-6400C3. The PCB of Dominator modules has a special copper-coated area at its top two additional aluminum heat-spreaders are fastened to. Thus, a Corsair Dominator module is cooled by a total of four heat-spreaders, two of which are responsible for the external surface of the memory chips and two more for taking heat off the module’s PCB which becomes hot receiving heat from the internal surface of the chips as well as through the contacts.
Thanks to this cleverly designed cooling system, it became possible to increase the voltage of the Corsair TWIN2X2048-8888C4DF memory to 2.4-2.5V. That’s how they reached an 1111MHz frequency with 4-4-4-12 timings using the same chips from Micron as are employed in other overclocker-friendly DDR2 SDRAM modules.
That’s not all about the cooling of TWIN2X2048-8888C4DF modules. There is an additional cooler included with the Dominator kit. It is fastened on the DIMM slot locks and blows at the installed modules to guarantee their protection against overheat.
This cooler contains three 40mm fans with a rotation speed of about 5000rpm. The fans are all directed towards the memory to ensure strong airflow there. The efficiency of this cooler is beyond any doubt, but unfortunately, its noise is audible, and this spoils the overall impression from the solution.
The cooler is shipped only with Corsair TWIN2X2048-8888C4DF kits so far, but the manufacturer is planning to sell it separately, too. As a matter of fact, it can be easily installed into almost any system.
Now that we’ve got some general impressions about the TWIN2X2048-8888C4DF, it’s time to check this kit out in practice. The testbed was configured like follows:
We assembled the testbed around an Intel processor for today’s tests because such systems are the more likely environment for the rather expensive PC2-8888 modules to be used in. Although fast memory would produce a bigger effect in Socket AM2 systems (the speed of CPU-memory communication is limited by the bandwidth of the FSB bus on LGA775 platforms), it won’t be used there often. After the introduction of Core 2 Duo processors, AMD’s CPUs have been relegated to the position of products for inexpensive entry-level and mainstream computers. Installing expensive memory into an inexpensive computer system doesn’t make much sense. There will be exceptions, though. Corsair itself tests its Dominator series modules on an ASUS M2N32 Deluxe mainboard that supports AMD processors.
Let’s take one more look at the modules before installing them into the testbed. Each module has a sticker with a module part number (CM2X1024-8888C4D) which differs from the part number of the whole kit. Besides that, the sticker shows you the frequency, capacity and timings of the module. There’s no voltage info here.
The modules’ SPD contains the following data:
The SPD information contains DDR2-533 and DDR2-800 modes for better compatibility with mainboards. It means you have to configure this kit manually in the mainboard’s BIOS Setup on your computer. The EPP data (Enhanced Performance Profile) may be of some help, but only on mainboards that are based on Nvidia’s chipsets. The EPP contains information about the single overclocked mode covered in the specs: 1100MHz, 4-4-4-12 timings and 2T Command Rate.
Tested at 2.4V voltage and with the cooler installed, the Corsair TWIN2X2048-8888C4DF kit showed the following results (the graphs show the highest frequencies the system was stable at for every set of timings). The stability of the system was verified by running three utilities: Memtest86, S&M and Prime95.
The diagram shows that the Corsair TWIN2X2048-8888C4DF kit is a versatile product, just like the rest of memory modules based on Micron chips. It can be used at frequencies up to 600MHz with as aggressive timings as 3-2-2-8. With 3-3-3-10 timings this memory hits the 800MHz mark. At its default 4-4-4-12 timings, the kit is operable at frequencies up to an impressive 1150MHz, providing a kind of safety margin above its specified 1111MHz. Setting the timings even higher doesn’t affect the frequency potential of the modules much. But even despite this, the Corsair TWIN2X2048-8888C4DF kit is to be acknowledged as the fastest DDR2 SDRAM kit for today. No other memory has ever performed like that in our labs.
It should be noted that the memory cooler supplied with Corsair Dominator memory doesn’t have a big effect on the modules’ overclockability. The cooler just guarantees good thermal conditions. Particularly, when we used the memory in its default mode (1111MHz with 4-4-4-12 timings), it was about 50°C hot without the cooler (under full load, on an open testbed and at an ambient temperature of 22°C) and only 33°C with the cooler.
Yet another curious fact we discovered in this test is that the frequency potential of the reviewed memory is greatly reduced when its voltage is lowered to 2.2V, which is the unofficial standard for a majority of other overclocker-friendly memory kits. For example, the Dominator kit was stable only as DDR2-1085 with 4-4-4-12 timings at this voltage.
Although Corsair was throwing around words like “the fastest” and the “world’s first” upon the announcement of its Dominator series, products with a similar specified frequency already exist. Particularly, they are offered by OCZ, a long-time rival of Corsair. Since early August there is PC2-8800 memory, OCZ DDR2 PC2-8800 Gold Edition, among overclocker-friendly DDR2 SDRAM modules supplied by OCZ. This memory was introduced without much pomp because OCZ’s engineers didn’t redesign the cooling system to achieve the 1.1GHz frequency. The fast memory from OCZ uses the well-known and time-tested XTC heat-spreaders (Xtreme Thermal Convection).
The XTC heat-spreaders ensure good heat dissipation thanks to their meshed design that enlarges the surface area. Besides that, the heat-spreaders are made of copper which has higher thermal conductivity in comparison with aluminum. Such heat-spreaders are capable of cooling memory chips clocked at 1100MHz and guarantee their stability and long service life as is confirmed by the lifetime warranty OCZ provides for all of its products.
The OCZ DDR2 PC2-8800 Gold Edition modules are also interesting for the fact that the manufacturer doesn’t declare the necessity to increase their voltage to 2.4V to achieve the record-breaking frequency. The voltage of the modules is specified as 2.2-2.4V, so they can be used at 2.4V, but do not normally require that voltage. In other words, the OCZ DDR2 PC2-8800 Gold Edition can be clocked at 1.1GHz at 2.2V voltage, but the manufacturer also guarantees the memory will work well at 2.4V, too.
The specification says the OCZ DDR2 PC2-8800 Gold Edition kit includes two 1GB DDR2 SDRAM modules that are to be clocked at 1100MHz with 5-6-6-15 timings and 2.2-2.4V voltage.
As you can see, the product from OCZ has worse specified timings, but not frequency, in comparison with the Corsair TWIN2X2048-8888C4DF. Corsair’s Dominator memory, equipped with an innovative cooling system, is capable of working at 1.1GHz with 4-4-4-12 timings whereas the OCZ DDR2 PC2-8800 Gold Edition with their XTC heat-spreaders can only work at that frequency with very relaxed timings of 5-6-6-15 (according to the specification). Externally, OCZ’s DIMMs don’t look as impressive as Corsair’s Dominator. Well, the gold-sputtered XTC heat-spreaders on the OCZ DDR2 PC2-8800 Gold Edition certainly have a good style of their own. A letter Z is embossed in the center of each heat-spreader as the symbol of OCZ. The stickers on the heat-spreaders tell you the part number, frequency and default timings of the product.
The SPD information of these modules describes DDR2-533 and DDR2-800 modes so that you could start your OCZ DDR2 PC2-8800 Gold Edition up on any system. Then you should go into the mainboard’s BIOS Setup to configure memory parameters as necessary. Unlike Corsair’s modules, the OCZ ones do not support the EPP.
We tested the OCZ DDR2 PC2-8800 Gold Edition memory on the same testbed as we used to check the Corsair TWIN2X2048-8888C4DF out. The graph below shows the highest frequencies the OCZ memory is stable at with different timings. The stability of the system was tested by running three utilities, Memtest86, S&M and Prime95. The memory voltage was set at the maximum value allowed by the specification, i.e. at 2.4V. The results are presented in the next diagram:
First of all, we should note that the OCZ DDR2 PC2-8800 Gold Edition kit is inferior to the Corsair TWIN2X2048-8888C4DF not only in declared, but also in real parameters. Its frequency potential is considerably worse than that of the Corsair Dominator at 4-4-4-12 and lower timings. At 3-3-3-10 timings the OCZ DDR2 PC2-8800 Gold Edition kit proves to be unable to work in DDR2-800 mode. At 4-4-4-12 timings, its max frequency is just a little over 1GHz. When the timings are more relaxed, the OCZ modules begin to behave more like Corsair’s Dominator. With 5-5-5-15 timings, for example, the OCZ memory is capable of working at frequencies up to 1155MHz. In other words, the OCZ DDR2 PC2-8800 Gold Edition modules stick to their specifications and conquer high frequencies only with high timings.
Unlike the above-described modules from Corsair, the OCZ memory remains stable in the default mode as well as at 2.2V voltage. It could work at frequencies up to 1116MHz with 5-5-5-15 timings and 2.2V voltage.
The leading manufacturers of overclocker-targeted memory modules, Corsair and OCZ, once again prove their highest technological and engineering potential. These two companies have introduced 1.1GHz DDR2 SDRAM modules ahead of all their competitors. However, this success was achieved by means of a long-known method, namely by increasing the voltage of the memory chips. PC2-8800 memory modules require 2.4V voltage, and this can be a cause of problems, particularly of higher heat dissipation that has to be coped with somehow. Corsair’s engineers introduced their revolutionary Dual-path Heat Xchange system whereas OCZ employed XTC heat-spreaders the company had tested on its earlier products. Both solutions proved to be adequate for the intended purpose.
The memory kits from Corsair and OCZ have somewhat different specifications. The Corsair TWIN2X2048-8888C4DF can be used at 1100MHz with 4-4-4-12 timings. The OCZ DDR2 PC2-8800 Gold Edition can only work at that frequency with 5-5-5-15 timings. So, the Corsair Dominator looks preferable from this point of view, but we should also take the price factor into account. The 2GB Corsair TWIN2X2048-8888C4DF kit costs as much as $650. The same-capacity OCZ DDR2 PC2-8800 Gold Edition kit costs $450 and looks as a value offering in comparison.
The Corsair TWIN2X2048-8888C4DF kit is worth its price, though. It is versatile in the sense that you can use it at 1.1GHz with rather low timings or as DDR2-800 with 3-3-3-10 timings. The OCZ kit can’t offer that. Besides, the Corsair Dominator kit includes a special-purpose cooler for cooling your DIMMs.
Winding up this review of recently released PC2-8800 memory, we want to draw your attention to the limited area of application of such memory, despite its impressive characteristics. Not all mainboards can give a voltage of 2.4V, necessary for PC2-8800, to the memory slots, yet this is not the main problem with such memory. What casts a doubt on the market perspectives of fast DDR2 SDRAM is the fact that today’s computers can’t “digest” it. As we’ve shown in our earlier reviews, overclocked systems with Core 2 Duo processors provide their highest performance when the memory is clocked in sync with the FSB. It means that you have to overclock the FSB to 550MHz for the expensive DDR2-1100 SDRAM to justify its cost. While it is possible with Core 2 Duo processors, considering that you can lower their frequency multiplier to 6x, modern mainboards can hardly work at such a high FSB clock rate, at least not until the release of a new revision of the Intel P965 Express chipset. As for computers with Socket AM processors from AMD, DDR2-1100 SDRAM may bring certain performance gains to them, but wouldn’t make sense from the economical standpoint. Today, platforms with AMD processors are entry-level and midrange solutions, so it’s unreasonable to use them with expensive top-end memory.