Review By John Grabski - January 30, 2005 Edited By Ed Piotrowski
SISOFT SANDRA TESTING
Some other reviews of this memory have shown it to not be able to perform at its rated frequency in an Athlon64 configuration. I refused to accept this notion and spent countless hours researching different BIOS revisions, timing nuances, and memory slot configurations. I had several beneficial conversations with Corsair technical staff. In the end,
this memory can perform at DDR550 speeds on an Athlon64 system, albeit with a 2T command rate. With 2T disabled, a Sandra 2004 bandwidth test revealed some awesome performance numbers (more than 7,100 MB/s in SiSoft Sandra), but regrettably, my system was unstable at these settings.
Before I fully dive into the Sandra performance figures, something must be mentioned about a couple factors particular to modern Athlon 64 setups. First, latency, while important for Pentium 4 and Athlon XP processors, is not such a huge factor for the Athlon 64.
For example...
I lowered my CPU frequency down to its stock 1.8 GHz/200 HTT configuration to check out how much latency matters on this platform. As it turns out, the performance hit taken when increasing memory latency is not anywhere near what it is with previous AMD chips. The integrated memory controller of the Athlon 64 seems to have quite a bit of flexibility, still allowing for quite reasonable performance at higher latencies.
The second factor is the 2T command rate. The A64 crowd is having quite a time with this setting, as it has been found out that when enabled, performance drops considerably. The K8NS Ultra-939 features three options in the BIOS for this: Enabled, disabled and auto. Leaving it disabled (or at 1T) can cause stability problems at higher clock speeds. This setting dictates the number of times a value is sent to the memory chip for execution. The 2T setting ensures the commands/values are sent and processed correctly through duplication.
As you can see, enabling the 2T command rate decreases performance by around 10 percent. Mind you, this is not a system-wide performance downgrade, but rather it's a chunk taken out of memory bandwidth potential. This should only be done for the sake of stability. Some other A64 rigs, and more than likely, any i875 chipset may be able to run at 275 HTT with 2T disabled and obtain similar performance.
PCMARK 04 TESTING
PCMark 04 is a well-rounded system benchmark program created by FutureMark. It runs a refined suite of tests similar to its predecessor, PCMark 2002.
Obviously there are improvements when looking at the results of this benchmark. Virus Scanning, DivX video encoding and Physics Calculation & 3D all experienced noticeable improvements. Worth mentioning is the fact that the tests showing the most improvements are ones closely tied to real-world system usage.
OTHER TESTS
Unreal Tournament 2004, a heavily CPU/RAM dependant game, was run at 640x480, with all details set to lowest. The 3dcenter.de timedemo "Primeval" was used as it is especially taxing on the CPU/memory subsystem. In stock configuration, the 3000+/5700 Ultra combination could not break the 50 fps barrier. Being already satisfied with the 53.14 fps the ValueSelect RAM gave me, anything more was just icing on the cake. The 2.5 fps improvement from the XMS was very satisfactory, again reinforcing the notion that enthusiasts can count on this memory to perform very well.
SuperPi has been used as a stability test and an excellent memory benchmark. I didn't expect any improvement, as the cpu's clock speed stayed the same, but was surprised with a one-second improvement. Once again this memory showed that it can help improve performance in demanding applications, even ones where improvements are hard-fought.
CONCLUSION
This is high end gamer memory with blazing fast performance, positively. And as it turns out, it runs at the rated speed on Intel AND AMD platforms. This is a big plus. Kudos go to Corsair for making a matched pair of high-end memory modules that are compatible with various platforms. These two modules may have only improved the review system's performance incrementally, but it's not like we started at ground zero, as the ValueSelect memory can still put up respectable performance numbers. But for PC enthusiasts looking to get every last megahertz, frame per second and benchmark point out of their systems, Corsair XMS 4400C25PT is a very competitive (and compatible) choice.
Special thanks go to Corsair for providing the review sample, and more specific thanks go to George Makris Corsair for going out of his way to help solve compatibility concerns.
