32- and 64-bit processing refers to the number of bits used to represent computation instructions in a CPU, as well as the number of bits used to represent memory locations in RAM. It has nothing to do with the color depth of an image.
Since at least Photoshop 4.0, the program has been written as a 32-bit application. When 64-bit computing became more mainstream, Adobe started making 64-bit versions of their software.
64-bit processors and software can work more efficiently with complex data like high-resolution images and large files. Since at least Photoshop CS5, most of the features have 64-bit versions so that the program can take advantage of the extra processing power. A few plug-ins and filters remain in 32-bit mode, and cannot be used in 64-bit mode.
Using 32-bit modeEdit
On Windows 64-bit operating systems, Adobe installs two versions of Photoshop:
- A native 64-bit version in the
- A 32-bit version in the
Program Files (x86)folder
To run 32-bit Photoshop on a 64-bit Windows system, run the latter option. You may need to create a shortcut to quickly access the 32-bit version.
On a Mac, the Get Info command in Finder allows you to select 32-bit mode for Photoshop.
- Photoshop CS5 plug-ins and technical differences between 32-bit and 64-bit software [Adobe]
- More on 32-bit versus 64-bit computing at Wikipedia