TechNote

64-bit Operating System benefits and limitations in Photoshop CS4 (Windows)

What's covered

Opening 32-bit and 64-bit versions
Third party plug-ins
Processor speed and Photoshop operations
RAM use

Photoshop CS4 installs both a 32-bit and a 64-bit version when you install on a 64-bit version of Windows Vista and Windows XP. If you are using the 32-bit version of Windows, then Photoshop only installs the 32-bit version.

If you are running Windows Vista, upgrade to Service Pack 1 for better performance.

Note: Although 64-bit Photoshop CS4 was not thoroughly tested under Windows XP64, and therefore is not supported, it should run.

Opening 32-bit and 64-bit versions

Photoshop installs a 32-bit and a 64-bit shortcut into the Start Menu. If you need to manually run the application, the 32-bit version is the photoshop.exe file, in the Program Files (x86)/Adobe/Adobe Photoshop CS4 folder, and the 64-bit version is the photoshop.exe file in the Program Files/Adobe/Adobe Photoshop CS4 folder.

Third party plug-ins

Third party plug-ins written for 32-bit versions of Windows will not work when you run the 64-bit version of Photoshop. If you need to use plug-ins that haven't been updated, run the 32-bit version of Photoshop. When you are done using the plug-ins, close the 32-bit version, and run the 64-bit version. Contact the plug-in manufacturer for information about any updates.

Processor speed and Photoshop operations

Although the 64-bit version of Photoshop will speed up some operations, it won't speed all of them, nor will it speed the operation equally. Generally, operations will run approximately 8-12% faster. Overall, processor speed is not the main advantage of using the 64-bit version.

RAM use

The primary advantage of using the 64-bit version is to access amounts of RAM beyond what Photoshop can access when the 32-bit version is run. You can take advantage of more than 4 GB of RAM only when you are on 64-bit Windows, using 64-bit Photoshop. If you use files large enough to need more than 4 GB of RAM, and you have enough RAM, all the processing you perform on your large images can be done in RAM, instead of swapping out to the hard disk.

This table lists the amount of RAM available to Photoshop with the different versions of Windows:

Photoshop Version	Windows Version	Maximum amount of RAM Photoshop can use
32-bit	32-bit	1.7 GB
32-bit	64-bit	3.2 GB
64-bit	64-bit	as much RAM as you can fit into your computer