need help with memory

well im planning on upgrading my memory to 2gb of ddr2 6400 cos my current 1gb cant handle an awful lot really.

how do you judge whether RAM is any good? i know what speed i want (800MHz) and i know the amount (2x1GB sticks) but i see a lot of things like "latency timings" which i dont really know about, with numbers like 5-5-5-15 or 4-4-4-12....which is better?

the stuff im planning on getting is from http://www.crucial.com/ because custom pc magazine say its the best mid range stuff for amd machines...what do you guys think?

the specificmemory is here: http://www.crucial.com/uk/store/partspecs.aspx?IMODULE=BL2KIT12864AA804

thanks.

The smaller the latecny, the better performance. The greater the Frequency, the faster performance.

I'd reccomend Corshair(I don't know if I worte it well).

4-4-4-12 is typical for PC2-6400 and 5-5-5-15 for PC2-8500. Like any latency, lower is better. It's basically how many nanoseconds it takes for the electrical signals on the memory chips to stabilize and execute a memory read access to send data to the bus to be read by the CPU. The more output buffers on the memory chip the longer this usually takes. DDR2 and DDR3 also takes longer because it's sending two and three times as much across the leading and falling edges of a memory access at one time.

These timings are actually controlled by your motherboard and as such the less time you give the memory to stabilize, the more stress you're putting on the circuitry of your memory. The EPD on the memory tells the motherboard what settings it should use to operate you memory optimally. Similar to overclocking a CPU, this generally requires more power to be fed to the memory modules to stabilize.