I have a 13" macbook pro, the low spec one, which has 2x1GB ram, I want to upgrade the ram, but I have a few doubts: 1 I often heard the term "mac compatible" ram, so what is exactly mac compatible ram? I only know my macbook pro uses DDR 3 1066 something ram, I found on internet other specs such as 200 pin, 240 pin, how do I make sure the ram is mac compatible? Or my macbook pro compatible? 2 As I have 2x1GB ram, if I buy 2x2GB ram, the 2x1GB ram will be wasted, it seems if I buy a single 2GB ram, only 1GB is wasted, but I wonder is 4G much better than 3G? I heard 2x2GB can make something called dual-channel, what is it? Is there any big difference? 3 Brand and Shop. I found several places which have DDR 3 Ram: Organizer World, , $49, Brand: Amicroe MLN. , they have 2GB DDR 3 for $99, Brand: Trenscend A Computer shop at Box Hill, on Whitehorse Road, they have 2GB DDR 3 for $58, Brand: Trenscend I wonder why the last two have such a different price, if they are all Trenscend? What is the best brand to choose? What store in Melbourne has best price/value? Thanks a lot!