Having some issues with mid sized (HD 720) PSD work and the scratch disc use. Settings in PS prefs are 70% (of 1.5GB). I know I could use some more RAM, but these PSDs are not HUGE, not like I'm doing print. Looking at the Apple Activity Monitor, PS is only using a small amount of available RAM. Something like 300MB of the 1.1GB (70% * 1.5GB) of RAM available to PS.
Any idea why the scratch disc activity (runs slow, writes to drive often) is so heavy when PS is not using all the RAM available to it? Anything I can do to optimize my system before I drop $$ on more RAM.