Change memory Latency time | Windows XP Performance Tips

If you do not intend to overclock your system much or at all, but would still like to squeeze out a little extra performance from your hardware, it's time to look at changing the latency settings of your memory. These affect the 'turnaround' time of your memory, how long it takes for the memory to prepare to send and receive data.

Understandably, lower latency times equal better memory performance, which in turn equals better system performance. Lowering latency times puts additional stress on your memory though, and may lead to system instability, especially if combined with overclocking.

Generally speaking, the higher the speed a memory module is rated for, the higher its latency will be. Hence, memory that is designed for overclocking will often have higher latency settings than 'normal' memory. There are four significant latency settings for modern DDR memory, listed here in order of significance:

1. CAS (Column Address strobe) Latency: The time between a data request and the data being made available. The most important value for SDRAM memory
2. RAS-to-CAS latency: Delay incurred by activating a new 'row' of memory addresses to read from. More important for DDR memory.
3. RAS precharge: How long a row of memory is held 'open' (powered) so that data can be read from it.
4. ACT to precharge delay: There are some things even us "experts" don't know - this is one of them ;-)

These values are often displayed as a set of four numbers illustrating the latency timing of the memory: for example, 2-2-2-5 (with the first number representing CAS latency.) These are either listed in the same order as presented above, with CAS latency leading, or with ACT to RAS precharge as the second number.

If these memory settings are available in your motherboard's BIOS, they should be in the 'advanced chipset options' section. Test your memory with lower latency values and benchmark if stable. For a slightly more in-depth look at the kind of memory you may need to have in your system to take advantage of CAS settings, please see PCstats article on Memory and CAS Latencies.

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