View Full Version : Photoshop CS3 RAM usage

01-25-2009, 12:02 AM
I am sure my question has been discussed somewhere in cyberspace before but cannot find an answer anywhere on Adobe or Google search.

I have a MacPro Quad with 16GB RAM.

In PS CS3 the Memory Usage in performance preferences only shows 3072mb as available RAM. Is this because CS3 only allows PS to access 3GB? If so, then it should be OK to set the slider to 100% as the other 13gb will be available to the OS?

Is there a plugin or software that allows PS to access more of the 16GB RAM?

Has RAM usage preferences changed in CS4?

I use "larger tiles" and the "Force VM buffering" plugins.


01-27-2009, 06:57 AM
Hi Strikey-

It's good that you are using the "Bigger Tiles" plugin; PS will perform faster that way. And it's also good you are using the Force VM Buffering plugin because that way PS will take advantage of all 16G of your installed RAM.

But be aware that if you are using 10.4 Tiger as your OS, you need the plugin active in order to buffer scratch data in RAM. However, if you are using 10.5 Leopard you don't need it active because 10.5 buffers scratch data in RAM by default.

By using the Force VM Buffering plugin, you can take advantage of all that extra 12G of installed RAM beyond the 4G set aside for PS when it's open. PS is still a 32bit app so it can access directly <only> a theoretical maximum of 4G of RAM...

In practice that 4G gets whittled down closer to 3G because PS is programmed to reserve a certain amount for use by the OS to execute PS's commands and for certain PS filter plugins that need dedicated, un-fragmented chunks of RAM when used...So you end up with PS offering you a maximum of "3072 MB" in the slider- exactly 3GB (even though PS really is reserving 4G for itself).

Though you can set PS to use "100%" on the memory slider, it's usually better to set it lower (like 70%) because PS will generally run more smoothly when the OS is given more than the required minimum amount of RAM to do Photoshop's bidding (that gets taken from that initial 4G allocation to PS).

So- with buffering enabled, you are taking complete advantage of your large amounts of installed RAM. VM buffering really speeds up operations with larger image files. With smaller image files, the entire image might be in RAM anyway, so in that case, it's operating at maximum performance to begin with.

RAM usage in CS4 is essentially the same as in CS3.

Once we have a native 64bit PS for Mac, you'll see an even bigger speed bump when large amounts of RAM are installed. The fastest Photoshop setup for Mac currently is CS4 running under Vista on a Mac Pro with 16+ GB installed RAM.

02-01-2009, 03:13 AM

Sorry I havnt been back to acknowledge your reply. Been busy on other things.

Ok so you have validated what I though was happening, thank you.

I am on 10.5 so will de-activate the "Force VM buffering" plugin.