Optimize performance of Photoshop...

The performance of Adobe Photoshop CS2 is affected most by available random-access memory (RAM) and computer processor speed. Other factors can also affect performance, such as the options you select, system configuration, and the built-in limitations of Photoshop. Photoshop CS2 supports new maximum image dimensions, and file sizes requiring increased system requirements. The maximum file size Photoshop CS2 supports is 300,000 x 300,000 pixels, except for PDF files, which are still constrained by the 30,000 x 30,000 pixel limitation.

Photoshop CS2 has an increased file size capability for the following file types:
-- PSD files: 4 GB
-- TIFF files: 4 GB
-- PSB files: 100 GB
-- PDF files: 10 GB (pages are limited to a maximum size of 200 inches).

Note: Large Document Format files (.PSB) cannot be read by Photoshop 7.0.x or earlier.

Adobe Photoshop options and plug-ins
The options you select and plug-ins you use in Photoshop can affect its performance. The options and plug-ins that most directly affect performance include those covered in this section.

Setting scratch disks
The Photoshop scratch disk is similar to virtual memory. For the best performance, you should set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds (rather than a network drive or removable media such as a Zip drive). Photoshop requires at least 650 MB of free hard-disk space, but more is recommended. If you have more than one hard disk volume, you should specify additional scratch disks. Photoshop CS2 supports up to 64 exabytes (EB) of scratch disk space on a total of four volumes. (An EB is equal to 1 billion gigabytes.) RAID 0 partitions provide the best possible performance as Photoshop scratch disks.

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Optimize performance of Photoshop (CS2 on Windows)

Optimize performance in Photoshop (CS2 on Mac OS)