The Reality of RAM

In theory, Photoshop 7 and Photoshop CS can use up to 2GB of RAM before resorting to active scratch

disk usage. In actual practice, 100% "Available RAM" in Photoshop 7 and CS memory preferences varies be-
tween about 1600MB and 1800MB in systems with 2GB or more of RAM. This is because Photoshop 7 or CS
"sees" only the first 2 GB of installed RAM, and- assuming this is the total amount installed in the machine, re-
serves a minimal amount of memory for the Mac OSX operating system.

Both Photoshop CS2 and Photoshop CS3 have larger RAM limits and additional sophisticated features
When used with Mac OS 10.3 or newer and 4GB of installed RAM, CS2 can use more RAM directly for image
data- up to 3072MB. An additional amount of RAM- approximately 600MB- is reserved especially for plug-ins,
filters, actions, and other operations that need large amounts of contiguous memory- bringing the total used
directly by Photoshop to roughly 3.7GB. Both CS2 and CS3 "see" only the first 4GB of installed RAM, and as-
suming this is the total amount in the machine, reserve a minimal amount of memory for the Mac OSX operat-
ing system.


For best performance, provide Photoshop and the Mac OSX operating System with as much RAM as possible.
Adding additional RAM to your machine is an excellent investment; it improves overall system performance
across a wide range of applications by reducing swapfile activity, and it allows Photoshop to keep more image
data in RAM for faster processing and less scratch disk use. Large amounts of installed RAM improve Pho-
toshop performance dramatically.