Mac slow after migration I just restored my old Late 2009 27" Quad core iMac, from Time Machine to a Late 2012 21" i5 iMac, and at certain points it is very slow and laggy. For example when I try to open Photoshop, or just randomly when I am on the browsing the Web using Google Chrome.

Nothing seems to be using too much of the CPU or the RAM, but maybe I need to do some kind of system clean. I already installed the newest OS which seems to have helped.

Can anyone please let me know what might be the best solution, or general steps which should be taken in this case.
It can take a while for a Mac to reindex all your files after an OS upgrade. Leave it powered on and mostly idle for a day or two, especially if your disk is nearly full. That will give it time to complete its background tasks.