The Columm Access Strobe (CAS), also known as CAS latency, describes how long it takes to read a column of a memory cell
. The Columm Access Strobe is the amount of time it takes
fora memory device to read the first data word after receiving the command and address
. The latency is a rating for the readout time and depends on the data rate of the motherboard's front side bus. The lower the value, the better. For example, a DIMM module with a CAS latency of 2 (CL2) is better than one with 3 (CL3). The same applies to the Row Access Strobe (RAS), the so-called RAS latency.