here s the spec of my MBP http://support.apple.com/kb/SP24 I am not sure if this is the Sta Rosa or not. I have the 15inches 2.33ghz. It came stock with 2GB of RAM. I see that Apple states the max of 3GB for this machine and from what I read here and on the internet, the machine will take 4GB, but only show 3.3GB or so due to the Intel chipset limitation. I recently installed 4GB in it and I am really puzzled at my machine. Not only does it show 4GB in "About This Mac" and in the System Profiler (which from what I read is normal) BUT it also shows 4GB in Activity Monitor. Now from my reading the Activity Monitor should show the 3.3GB, but mine shows 4GB. I have two thoughts on the issue. One is that possibly a firmware or software update along the way raised the limitation and it hasn't been mentioned. Two is that there was a silent hardware revision and that some of the machines that are supposed to be limited to 3GB are actually truly capable of 4GB. My question: Can someone explain to my why my machine shows all 4GB in use when it should be limited to the 3GB? Thanks.