Photoshop displays the RAM available to Photoshop and the ideal range of RAM for Photoshop (a percentage of the total available RAM) in Performance preferences.
Allocate RAM to Photoshop
For detailed information on improving Photoshop performance, including specifying RAM settings in preferences, see Optimize performance | Photoshop CS4, CS5 (kb404439) in the Adobe support knowledgebase.
Assigning scratch disks
When your system does not have enough RAM to perform an operation, Photoshop uses a proprietary virtual memory technology, also called scratch disks. A scratch disk is any drive or drive partition with free memory. By default, Photoshop uses the hard drive on which the operating system is installed as the primary scratch disk.
Photoshop detects and displays all available internal disks in the Preferences panel. Using the Preferences panel, you can enable other scratch disks to be used when the primary disk is full. Your primary scratch disk should be your fastest hard disk; make sure it has plenty of defragmented space available.
The following guidelines can help you assign scratch disks:
For best performance, scratch disks should be on a different drive than any large files you are editing.
Scratch disks should be on a different drive than the one your operating system uses for virtual memory.
RAID disks/disk arrays are good choices for dedicated scratch disk volumes.
Drives with scratch disks should be defragmented regularly.
Change the scratch disk assignment
If Photoshop cannot launch because the scratch disk is full, hold down the Cmd + Opt keys (Mac) or Ctrl + Alt keys (Windows) on launch to set a new scratch disk.
Specify history and cache settings
Specify the maximum number of History States that appear in the History panel.
Specify the Cache Levels and Tile Size for image data. To quickly optimize these settings, click a preset for images with these characterstics:
Tall and Thin
Many layers and small dimensions.
Moderate dimensions and layers.
Big and Flat
Large dimensions and few layers.
You must restart Photoshop to apply new cache settings.
The Purge command lets you free memory used by the Undo command, the History panel, or the clipboard.
- Choose Edit > Purge, and choose the item type or buffer you want to clear. If it is already empty, the item type or buffer is dimmed.
The Purge command permanently clears from memory the operation stored by the command or buffer; Purge cannot be undone. For example, choosing Edit > Purge > Histories deletes all history states from the History panel. Use the Purge command when the amount of information in memory is so large that Photoshop performance is noticeably affected.
Enable OpenGL and optimize GPU settings
OpenGL is a software and hardware standard that accelerates video processing when working with large or complex images such as 3D files. OpenGL requires a video adapter that supports the OpenGL standard. Your performance when opening, moving, and editing 3D models is significantly improved on a system with OpenGL. (If OpenGL is not available on your system, Photoshop uses software-based ray-trace rendering to display 3D files.)
If OpenGL is present on your system, you can enable it in the Preferences dialog box.
For more information, see: