Ad-hoc and generalized guidelines exist for optimizing Photoshop performance, but relating a particular workload size to memory and scratch volume requirements is usually left as an “exercise for the reader.
I will present specific and actionable research into Photoshop CS4 performance on the Mac Pro and MacBook Pro (most of which applies to Windows PCs as well). Processing time can be cut by as much as 80% by appropriate choice of the amount of memory and the speed of the scratch volume, and by some key configuration parameters of Photoshop itself. Compare that to the modest 14% speed difference and huge cost difference of a 3.2GHz versus 2.8GHz Mac Pro.
Workloads that force Photoshop to swap image data to and from the scratch volume include not only very large files, but also files with many layers, steps, or operations. With these demanding f iles, overall processing time is influenced far more by adequate memory and fast hard drives than by CPU speed. CPU speed does matter when executing Unsharp Mask or Gaussian Blur or similar filters with the entire image in memory. Once the image cannot be held in memory, CPU speed is a minor point.
(For more information on many areas covered here, see MacPerformanceGuide. com, or MPG, a Web site I’ve created to cover these issues.)
The research conducted here used a medium and large Photoshop “action” (script) composed of operations chosen to stress the memory requirements of Photoshop. Two benchmarks were used: diglloydMedium and diglloydHuge. Upon completion, the diglloyd Medium action results in a 15.6GB scratch f ile, and diglloydHuge results in a 56.4GB scratch f ile. You can download the benchmarks at MPG.