The most important RAM timings are CAS latency (CL), RAS-to-CAS delay (tRCD ) and RAS precharge time (tRP ). Many memory modules have specifications such as PC2700-2.0-2-2.0 or PC3200-3.0-3-3.0. The first of these seemingly inscrutable numbers describes the memory type, the latter three the aforementioned timings. Other manufacturers merely list the CAS latency as CL 2.0 or CL 3.0. While it is an important performance feature, not listing the other parameters is a big disadvantage for the buyer because each one has a similar impact on system performance.

To see for yourself how big this impact is, take a look at the performance benchmarks for MPEG-4 encoding. We've also included a brief run-down of the most important timing parameters, short explanations and tips on the best settings at the end of the article, under the heading "How to Tweak Your RAM in BIOS." If clear information on possible performance settings is conspicuously absent from your brand-name RAM, you can consult the data sheets on the Internet (see "RAM Manufacturers").

To better understand the timing parameters, you should know about everything involved in accessing memory. The "RAM Timings" chart will give you an overview of how it works. A read process is initiated when the controller in the motherboard chipset selects the memory module that contains the data. The controller addresses the right chip on the module and the data it holds. The cells of the chip are arranged in a matrix and are addressed using the row and column addresses. Each intersection represents one memory bit.