The memory usage and history and cache preferences offer you control over how much RAM is assigned to Photoshop. It also lets you set how much memory is alocated to screen redraws (Image Cache). Photoshop is a high-performance application that requires a large amount of RAM. Photoshop also uses many operations that affect RAM - History States, Undo, Clipboard, and Cache. The Cache Levels are screen redraws, or or the many versions of the current active image or called by Photoshop document Photoshop saves. If you are working on large documents, more Chache Levels help speed up the redraw functions, and make image manipulation go faster. This is help mostly in RAM, so the more Chache Levels you choose the less RAM is avialable for other Photoshop functions. The Cache is the amount of data Photoshop stores or processes at once. Use a larger size for larger documents to speed up processing. When you are unsure what to set use one of the preset buttons. Refining Photoshop's enging will increase its overall speed.
Memory and Image Cache:
For Windows - Edit > Preferences > Memory & Image Cache Options
For Mac - Photoshop > Preferences > Memory & Image Cache Options
• Select the History & Cache options you want to use:
○ To Optimize. Click a button to use a preset cache level.
- Tall and Thin. Use for small documents and many layers (dozens to hundreds).
- Default. Use for general use.
- Big and Flat. Use for large documents (hundreds of megapixels) with few layers.
○ History States. Enter the amount of History States steps you want to keep as undos; you can enter up to 1,000. The more History States used, the more RAM is required, which impacts performance.
○ Cache Levels. Select a number from 1 to 8. Set to 2 or more for optimum GPU performance.
○ Cache Title Size. Specify a size for the amount of data Photoshop stores or processes at once. Use a large amount for large documents to maintain a good processing speed.
• Enter the percentage of RAM used in the Let Photoshop Use box.
Photoshop needs about 5 times the size of the open document of unused RAM to operate efficiently.
You should never select 100% Memory Usage for Photoshop, which leaves very little for the operating system or any other open programs. Changes made for allocating memory and image caching will take place the next time you start Photoshop.
• For installed video cards, the video card name appears. Select the Use Graphics Processor check box (New to CS6) to use the enhanced speed and smoothness of graphic/3D rendering and navigation. Click Advanced Settings to select additional options:
○ Drawing Mode. Select a mode (Basic, Normal, or Advanced) to use different amounts of memory processing (New to CS6).
○ Use Graphics Processor Computation Use OpenCL. Select to access available parallel processing power.
○ Anti-alias Guides and Paths. Select to enable anti-alias for better display (New!).
• Click OK to set your preferences.