How to monitor CPU core usage? I have a Macbook Pro 15" with the quad core i7. I am looking to see what if any performance decrease I could expect moving to a 13" Macbook Pro with a dual core i7. To that end I thought Activity Monitor might be able to show how many cores are being utilized while I run through various tasks (VMWare, Photoshop, etc ..). 

Does anyone know how to display core usage via Activity Monitor?
You can get a graph per core to show by going to Window on the menu bar and selecting Cpu Usage or Cpu History. There is also an option under the View menu to place a similar graph in Activity Monitor's dock icon.

If you're using a reasonably new Mac, Hyper Threading is enabled, so you'll see twice as many graphs as you have physical cores.