What does CL2 in RAM mean?

Answer 1

CL refers to CAS Latency or Column Address Strobe Latency to give it its full title. Basically the figure indicates the performance of the RAM module, the lower the figure the faster the RAM. In Synchronous DRAM this value is given in clock cycles, with Asynchronous DRAM is is given in nanoseconds.

Memory modules contain many memory chips. Each of these has memory portions arranged in rows and columns in a rectangular fashion - a bit like individual pigeon holes, each hole contains a portion of memory holding a small amount of data. In particular the CAS Latency value is the time it takes data in any given portion of the memory chips to become available to the modules output - how quickly the memory module gives up its data to the motherboard interface if you like.

There are 4 main measurements in evaluating memory performance, CAS latency is generally used as the standard measurement of a memory modules performance but this is not the full story. Row Address to Column Address delay (the time it takes to read the first piece of data), Row Precharge Time, and Row Active Time all indicate different aspects of the memories performance. It's like using the top speed of a car as the only measurement of its performance, a fast top speed doesn't mean a quick 0 - 60?

In general terms these are all referred to the memories "timings", lower values are always better..