this is copied from the crucial website explaining what Latency is...
CL=2 vs. CL=3
In general, CL=2 is better than CL=3, particularly if you are a gamer or have a high-performance system. However, if you are an average user, you probably won't notice the difference between the two parts. (CL stands for "CAS latency," which is the number of clock cycles it takes before data starts to flow once a command is received.)
When I was on the phone with crucial, the rep told me that in general, the CL=2 chip runs about 10% faster compared to a CL=3 chip. This obviously requires you to have all of your chips to be the same latency in order for your system to have that performance increase. If your Mac came shipped with a CL=2 chip and you bought a CL=3 chip, it could actually slow you down!
The current web price for a 256mb PC133 CL=2 SDRAM from crucial is $41.39 plus sales tax (if required), and no shipping charge if you are willing to wait about 3 days. Their 512mb chip is way overpriced at $269.00.
Another related, but similar subject:
I was sorting through some old papers and ran across an apple article about the Sawtooth G4. It has 4 memory slots instead of the 3 of the newer G4s. Apple says that the hardware will support up to 2 gb of SDRAM, but that the
Operating System will not.
So the question is, will Mac OSX support up to 2 gbs of memory? And when will the mac hardware support 1g chips?