Corsair TwinX1024 3200XLPro DDR DIMMs are blinders

THE BANE of DRAM wasn't always bandwidth, which you could increase by wider buses, interleaving, synchronous or DDR clocking, Rambus protocols and so on, but latency. Latency many times slower than that of SRAM, not to mention the on-chip SRAM caches on processors these days. And, no matter how fast you clock the RAM, or how wide the bus is, it is the latency of that critical first-word access in the burst that still matters - since every added RAM clock can be ten or twenty more CPU clocks wasted on wait.

Even though CPUs with out-of-order or multithreaded capability can simply attempt to do something else while waiting for the RAM, why not give some credits to those trying to mitigate the latency problem? Well, Corsair was the first last year to have a limited run of DDR400 memory at 2-2-2-6 latency settings, and now it is at it again, with their top model, TwinX1024 3200XL Pro.

These two black 512 MB DIMMs, with twin rows of multicoloured "load" LEDs on the top, are a sight to behold during operation, especially if you have a transparent casing and one of those funky boards like the MSI 875P Neo with lit-up NorthBridge chip. The larger heat spreader surface area also helps spread heat wider during long hours. More importantly, they specify the unbeatable 2-2-2-5 latency at DDR400 clock, the very maximum you can push the spec to.

To verify this, I tested the DIMM pairs in two suitable high-end configurations, both based on MSI boards: one was an Intel Pentium 4 EE 3.2 GHz, my reference benchmark system these days, whose 875P Neo board is finally very stable with the recent BIOS update; the other one was the new 2.4 GHz AMD Athlon 64 FX-53 939-pin vertion. Both ran 32-bit Windows XP SP1, and I checked the PC Mark 04 memory results, as well as Sandra 2004 Memory benchmark.

Pentium 4
Sandra Mem Int 5095 MB/s
Sandra Mem FP 5098 MB/s
PCMark04 Mem 5415

Athlon64
Sandra Mem Int 6004 MB/s
Sandra Mem FP 5944 MB/s
PCMark04 Mem 5667

Wow, for the first time, I see Sandra jump over 6 GB/s on an non-overclocked DDR400 dual-channel platform! The combination of Athlon 64 superior on-chip memory controller and Corsair's world's lowest-latency DDR400 memory works wonders - this is 93% of the peak theoretical 6.4GB/s bandwidth! Even on the Intel 875P chipset, the Sandra easily exceeded 5GB/s, an excellent result for that platform.

There is an argument that, with larger CPU caches, the memory latency may not be so important - true, it depends on the applications, though. When it comes to main memory, some are latency-sensitive, others are bandwidth-sensitive and, well, quite a few don't care as they are cache friendly! However, if building a top-notch PC and spending loads of cash on other components, you may as well also get the memory that will not only make others talk about it, but also, most probably, put to shame all DDR2-400 and many DDR2-533 configurations at a far lower price. Well, there it is! µ