photoshop is a 32-bit application so it can only address 3gb of ram.
note there is a slight difference in the amount of ram that a ‘foreground’ process can use vs. a ‘background’ process. on osx a 32-bit foreground process is limited to about 3gb, a background process is around 3.5gb. photoshop is a foreground process, while the ae render engines that get used when ‘render multiple frames simultaneously’ is enabled are background processes, so they can grab a bit more ram.
having more than 8gb would allow you to run photoshop and ae, each with their own chunk of ram which can make working with multiple applications much smoother. however, with only 2 cores, one core would get shared by ae and photoshop. so, say you are rendering in ae with multiprocessing enabled, and switch to photoshop to do some work. you’ll probably notice a some lag when manipulating the image or applying filters in ps… in situations where you know you’ll want to use ps while ae is rendering, you may want to disable mp in ae to get better performance in ps…
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW