the data in the memory is excessed by processor after immediate looking in the L1/L2 and L3 caches.
as the data in DRAM is in the form of rows and columns just like microsoft excel stores data in form of rows and columns, as if you want to excess some particular data, you say like that data is on 3rd row and 4th column (isnt it?)
same process is in PC, as when processor requires data, it sents CAS (Column Address Strobe, as told by TheMajor) and RAS (Row address Strobe) Signals to the memory Module to activate that particular memory cell.
now on the same basis as in excel, the CPU sents the RAS signal first, and on that particular row activation, it then sents the CAS signal to achieve that 1 cell's data.
and of course CAS lower is better, means that as if its 3, it takes 3 milli seconds to activate that strobe, and if its 2/2.5. it takes that much time.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"