When most people hear the term "overclocking," they immediately think of boosting CPU speeds. But another major speed factor is the FSB clock, the speed of which is easy to boost with little effort, delivering a performance jump that equals a few more MHz on the CPU. Still, speculation about the benefits of overclocking often become idle musings, especially on Pentium 4 systems, where the added benefit of the fastest RAM isn't always evident.

There's nothing fundamentally wrong with using the fastest possible RAM. The maximum attainable clock rates and related timing settings help to distinguish these elite products. In the case of an Athlon 64, this means using DDR400 DIMMs (with an FSB clock rate of 200 MHz), which should support ideal timing values of CL2-2-2-5. But you'll also find offerings on the market with more headroom for overclocking, where FSB rates of 500 MHz and higher may be feasible as long as other parameters remain workable.

In the case of a P4 system, DDR2 RAM comes into play. It's capable of running noticeably faster than conventional DDR, and its timing settings may likewise be trimmed as well. DDR2-533 (266 MHz) is firmly established today, and memory modules for 333 MHz (DDR2-667) are becoming more widely available. Anything faster than that is only achievable at present through overclocking, even with the chipset vendors keeping their silicon production firing on all cylinders.

You might be inclined to believe that the higher overclocking potential of DDR2 RAM might translate into measurable performance gains, but sadly, that's not necessarily true. In real-world situations, a P4 system running DDR2-533 is only slightly faster than one running DDR400. Likewise, stepping up to DDR2-667 produces less effect than you might desire.

In the meantime, an increasing number of vendors, such as A-Data and Corsair, are bringing DDR2-667 products to market that work with tight timing settings and elevated FSB clock rates - but even then, only using leisurely parameter values. We put actual DIMMs from both vendors under our microscope in an overclocked P4 system, to see what happened when DDR2-1066 clock rates are used.