SUMMARY: With modern motherboards continuing their push to the next level, it can sometimes be difficult to find memory that is up to the task. Come join Asher "Acid" Moses as he takes a look at the newset offering from Corsair; namely their XMS3200 DDR Memory Modules. They're marketing it as capable of delivering DDR400 compatibility with CAS2 Latency Timings. That's a pretty big claim, so come join us as we find out if it can really perform at this level!
A DDR memory module is given two names according to both its maximum transfer rate and speed. In the case of Corsair's XMS3200, its two ratings are PC3200 and DDR400. PC3200 is the maximum transfer rate of the module, which in this case is 3.2GB/sec. On the other hand, DDR400 is the speed of the module in MHz, which in the case of DDR400 is 400MHz (200MHz DDR).
The effective bandwidth of the module is worked out by taking its speed rating (400) and multiplying it by 8. We multiply the speed rating by 8 because DDR modules are 8 bytes wide. So, the formula for Corsair XMS3200 memory would be: 400 * 8 = 3200 or PC3200.
- The quest for CAS2 DDR400
CAS latency is the time delay that passes before the memory module carries out a command. Put simply, the lower the CAS Latency selected, the higher the performance, due to the fact that the memory will carry out tasks quicker. Until recently, memory manufacturers have been unable to produce CAS 2 DDR400 memory modules and have had to bump CAS timings up to 2.5 in order to run at DDR400 speeds. The performance difference is quite noticeable and is precisely the reason why we have seen DDR400 performing slower than DDR333 modules.
Corsair has finally managed to produce DDR400 modules that they say are capable of running at CAS ratings of 2-3-3 with a 1T command rate when running at 200MHz (400MHz effective), and 2-2-2 with a 1T command rate when running at 166MHz (333MHz effective).
- The Module
The first thing you'll notice about the module is that it is covered by a sleek black heatspreader. As far as I'm concerned, this is simply just a marketing tool as from our internal testing, we have found that the difference in temperature is negligible. However, as long as it doesn't raise the price of the module, we can't really complain now can we!
We've already discussed the module's CAS latency settings and speed ratings above, however, what we haven't discussed is the brand and type of memory used. To run with such a low CAS latency at DDR400 speeds, the highest quality, handpicked memory chips are required. Corsair has decided to use Winbond's Revision B 6.0ns chips on the XMS3200 modules, and have put each one through exhaustive tests to ensure that it can run at its specified ratings.
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