Dual Data Rate 2 or DDR2 memory is relatively new, and follows the introduction of Intel's LGA 775 socket and accompanying chipset architectures, as well as subsequent support for DDR2 in the AMD AM2 socket architecture and its accompanying chipsets. DDR2 has been in circulation for over three years as we write this article, and is the prevailing type of memory used in new computing equipment currently on sale in retail channels.

Table 3: Common DDR2 Memory Speeds and Nomenclature

Though PC2-3200 falls within JEDEC specifications, you hardly find it in actual use on desktop PCs (perhaps because it's the same speed and data rate as DDR-400/PC-3200). Our standard coverage concentrates on PC2-4200, -5300 and -6400, because those are the most commonly purchased varieties (even PC2-4200 memory can be hard to find). According to our vendor sample, in fact, PC2-5300/DDR-667 is the most-popular type of memory in the marketplace today. As in the preceding section, we cover performance DDR2 memory at the higher echelons of the price spectrum.