While at one point it -WAS- true that Photoshop needed 3 times to 5 times the file size in ram, that is no longer the case.

Prior to Photoshop 3.0, you could have enough ram installed so that Photoshop would not need to create a scratch disk. Depending on your Photoshop “buffers”, you needed 3x to 5x to be sure you could keep an image “all in ram”. If you did, Photoshop’s performace was much faster because it didn’t need to create a scratch disk. Photoshop buffered one current state, one undo state, one snapshot state, and potentially one Pattern state as well as the actual image. So, potentially you would need up to 5x the image size in ram.

With Photoshop 3.0, the memory mangement was re-written to -ALWAYS- create a scratch disk upon the launch of Photoshop. At this point the old “3x-5x ram” became a myth. With Photoshop 4 came image caching that altered the potential ram requirements and with Photoshop 5 came multiple undo (History) which, while it doesn’t alter the ram requirements, substantially altered the potential scratch disk requirements for Photoshop.

How much ram does Photoshop need? As much as you can shove in your computer. Even though Photoshop CS’s ram allocation is limited to 2 gigs minus a ram footprint for the application (several hundred MBs), having more ram installed benefits Photoshop by cutting down on system memory disk swapping. For most computers (both Mac OS X and Windows) having more than 2 gigs will show an improvement even though Photoshop can only directly access under 2 gigs.

This will change in the future, but for Photoshop 7 and CS, more than 2 gigs can help.

For more information about ram use in Photoshop CS, see this PhotoshopNews article.

This story was posted on Thursday, March 24th, 2005 at 2:23 pm and is filed under Facts & Myths. You can follow any responses to this story through the RSS 2.0 feed. Both comments and pings are currently closed.