Just wondering if anyone can point to where the slowness I'm getting is likely to be: Dual 6 core 3.06ghz in 4,1 -> 5,1. 48GB of Ram, Original GT120 GPU, no SSDs, running Yosemite using Photoshop CS 5. Photoshop files are 300-600mb in size, with 20-50 layers, layer effects, masks etc. All report 100% efficiency, which should mean they're fitting into ram & not using any scratch. The problem is zooming, moving & rotating around using trackpad - do a pinch to zoom in, it zooms a bit, then halts for 10-20 seconds, before completing the zoom. Same for rotation, only about half the duration of the gesture seems to be seen / acted upon. I'm thinking either there is scratch being used and the drives are slowing it down, or the GPU doesn't have the ability to drive the viewport changes, or CS5 is old enough that it's ability to respond to trackpad gestures is primitive & inefficient... or a combination of all 3. Anyone solved a similar problem?