What is CAS Latency in RAM

[hotdogXP]

I wanted to get a 512 MB DDR 400Mhz RAM and was going through a few online shopping sites, they have specified a parameter in the specs of the RAM called "CAS Latency" , the value varying from 2.5 to 3.5 for different RAMs of the same make and Mhz.

Is it related to any performance factor of the RAM and should I take this parameter into consideration when I want to buy it. I already have a 512MB 400Mhz installed in my system and in the BIOS it says the CAS Latency of this RAM is 3.0, should I get the additional 512MB also with the same value to work them in Dual channel config.

[phatratt]

CAS stands for Column Access Strobe.THe data is stored in columns and accessed in nanoseconds which varies from 2 to 3.5.

Googled it and got some info

http://www.dewassoc.com/performance/...as_latency.htm