Photoshop Performance Tips

Is Photoshop running sluggishly on your computer? Regardless of your system, these twelve simple steps will help you get the best possible performance from Photoshop:

In Photoshop preferences, set the RAM Usage to 75% and never higher.
In Photoshop preferences, set the primary scratch disk to a fast drive that is not running Photoshop or the System.* The scratch disk should also not be the disk drive onto which you are saving the working file.

I strongly recommend using an external FireWire/1394 or USB 2.0 drive specifically for the scratch disk only.

If you are currently using only one hard drive, you should consider buying an additional, inexpensive 60-80 GB drive for a scratch disk.

*This single change could make the biggest difference in the performance of Photoshop.
In Photoshop preferences, uncheck Export Clipboard.
Before starting Photoshop, quit all programs and system processes that are consuming significant system resources.
In Photoshop preferences, uncheck the Font Preview Size option.
In Photoshop preferences, set the Cache level at 6 and the History states to no more than 10.
Before performing a CPU-intensive operation (like a gaussian blur or sharpening) first Save the file.
When doing a CPU intensive operation that you need to preview, first reduce your preview size in the Photoshop window, so that the preview and redrawing operations do not need to cover such a large area on the screen.
Be efficient with your use of layers and layer groups; especially when there are lots of variations in layer or object transparency.
When moving layers between files, use Drag and Drop instead of Copy and Paste.
Sometimes it's faster to merge your visible layers to a new, single layer, put that in a new document, and then run the command there. Afterward, bring it back into your master file.
If you are confident that at a certain point you don't need your saved history, run the Purge All command from under the Edit menu.