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Work around Photoshop's 3GB RAM limit
Authored by: styrafome on Jul 19, '08 09:28:45AM

perspixe is correct! This hint is actually 100% unnecessary. Photoshop and OS X already do this on their own. If you have more than 4GB RAM, Photoshop will automatically ask OS X to use unused upper RAM as a scratch disk.

It is all automatic. It can grow as needed, whereas if you make your own RAM disk its size is locked. Let OS X do what it is designed to do for you.

This article explains how it works, with quotes straight from Adobe engineers:

Photoshop CS2 - How Much RAM

One quote from the article:

"We've seen 40% and greater speedups when running tests on big documents that hit the scratch disk by increasing RAM from 4GB to 6GB...What's happening is that Photoshop can only make direct use of about 3.5 GB of RAM on Mac and 2GB on Windows and 3+ on XP 64 bit. But when it goes to write to the scratch file, normally that I/O is done directly from Photoshop's memory to the disk (or vice versa). If you've got more than 4GB of RAM, we let the OS do its buffering thang instead. That is, data is not written directly to the disk; the OS copies it into RAM buffers that reside in that extra RAM Photoshop can't otherwise use."

Tiger is a little buggy about this, so you might need the Force VM Buffering plug-in to make it work. But Leopard seems to have fixed the problem.

Don't bother searching for Ramon Castaneda's posts on the Adobe forums. While he knows about this, he is only repeating documented information from Adobe. Second, every other thread he participates in over there turns into a lengthy, personal flame war thread that you don't want to wade through. Just get your information from the definitive source link above.

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Work around Photoshop's 3GB RAM limit
Authored by: perspixe on Jul 19, '08 03:30:59PM

Styrafome, thanks for finding this clear explanation and post it. I actually read it before but could not find it back. I never really noticed about Castaneda's flame but it seems that mention of his name is already creating some. I'll be more careful in the future ;-D

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