Hi all, This is my first post but been reading around the web mixed opinions as to whether its possible to install 1333Mhz RAM into a Late 2009 iMac 27". Well i can say that i had quite a result on this one. I managed to find a seller on eBay UK that was auctioning on a BIN (BuyItNow) 4GB 1333Mhz 204 Pin Unbuffered, PC3-10600 DDR3 RAM. Well after taking out my old 1066Mhz 4x2GB sticks and replacing with the above i can say that it is working extremely well!! I have added some screen shots of System Profiler If anyone has any comments about this or would like to share there experience of carrying out this upgrade i would like to hear about it. Thanks for looking! Chris.