"Photoshop can use a maximum of only 4GB of RAM. This limitation is imposed by hardware and the operating systems, among other things that only geeks and engineers with degrees in astrophysics understand fully. Suffice it to say, if you have 4GB of RAM installed, or more, you can safely increase the RAM allocation to 70%. Doing so will ensure that Photoshop uses as much RAM as it possibly can, up to the 3.7GB limit (or thereabouts, because the OS will reserve some of the 4GB for itself). If you do not have more than 4GB of RAM installed, you should reduce the allocation to something like 50–60%, especially if you are experiencing slow performance in Photoshop, which includes Camera Raw. To allocate RAM, go to Preferences>Memory & Image Cache and specify a percentage in the Memory Usage section of the dialog box (Figure 9)."
Posted by danklife at January 19, 2006 02:03 PM