I just got my 24 iMac 2.8Ghz last week and yesterday, I upgraded my RAM to 4GB RAM 800MHz SODIMM Kingston(2 slots of 2Ghz) from the stock 2GB RAM. Right after that, I restart my Mac and Mac recognizes my 4GB RAM input. But comparing speed between both is not much of a difference, specially boot up, or watching movie. I haven't start off with works of photo editing.(the reason i got a Mac) Can anyone here know what is the best way to know the speed difference or any difference?