Ps CS3 isn't recognizing all my RAM?

[SloYerRoll]

I was in another thread looking up something and stumbled over the fact that Ps doesn't seem to recognize all my RAM.

The screen grab below is my Ps settings on the left and my system settings on the right. So PS only thinks I have roughly 1.7GB of RAM while my system recognizes 3.6GB of RAM.

Any Ideas?

[DavidTO]

That's the RAM available to CS3, not the total RAM available to the computer, if that makes sense. On my mac I've got 4GB RAM, but only about 3GB available to PS. Not sure how the math works in Vista.

[Richard]

I was in another thread looking up something and stumbled over the fact that Ps doesn't seem to recognize all my RAM.

The screen grab below is my Ps settings on the left and my system settings on the right. So PS only thinks I have roughly 1.7GB of RAM while my system recognizes 3.6GB of RAM.

Any Ideas?

32 bit Windows has a maximum application address space of 2GB. However, Photoshop's virtual memory scheme does allow it to take advantage of additional RAM (to some extent). It will treat additional RAM as swap space, but instead of going out to disk, it will look in RAM. Unless you are working with extremely large files or many, many layers or history states, you should be fine. You can monitor it by setting the little info box at the bottom of the editing window to efficiency. If it stays at 100%, that means that you are not physically swapping to disk.

[SloYerRoll]

In that case why wouldn't I want to max out how much RAM I allow Photoshop to use? (as far back as I remember, Ps always recommended only 75% of available)
If this is the RAM that's available for PS to use and not diving into critically used RAM. Why not give it all it can take?

[Richard]

In that case why wouldn't I want to max out how much RAM I allow Photoshop to use? (as far back as I remember, Ps always recommended only 75% of available)
If this is the RAM that's available for PS to use and not diving into critically used RAM. Why not give it all it can take?
Some of the 2GB is actually reserved by Windows for its own purposes. I think around 1.6 or 1.7 GB is the most you actually get, so setting PS to higher than that doesn't actually do anything. There is a BIOS switch you can set in XP Pro SP2 that will extend process memory to 3GB, which PS will then recognize, but apparently it also breaks some device drivers. MS says proceed with caution, which to me says, for masochists only.

This is complicated stuff, and I don't understand all of it. There is a good overview on Adobe's Tech Note site on how to optimize CS3 performance on XP and Vista. (http://kb.adobe.com/selfservice/viewContent.do?externalId=kb401088)

[SloYerRoll]

Some of the 2GB is actually reserved by Windows for its own purposes. I think around 1.6 or 1.7 GB is the most you actually get, so setting PS to higher than that doesn't actually do anything. There is a BIOS switch you can set in XP Pro SP2 that will extend process memory to 3GB, which PS will then recognize, but apparently it also breaks some device drivers. MS says proceed with caution, which to me says, for masochists only.

This is complicated stuff, and I don't understand all of it. There is a good overview on Adobe's Tech Note site on how to optimize CS3 performance on XP and Vista. (http://kb.adobe.com/selfservice/viewContent.do?externalId=kb401088)Thanks Richard,

I've pored over this doc and I don't see anywhere where it says what happens if you set RAM allocation higher or lower. It just says "let photoshop pick" which is 75% of available RAM. I did a test and took out 2GB of RAM and tried again and it was still 75% of available. So it seems this 75% is a static number. :scratch

Has anyone out there goofed w/ RAM allocation settings in PS and seen a difference? :ear

[colourbox]

This article might have more details (http://photoshopnews.com/2005/04/04/photoshop-cs2-how-much-ram-fact/) than the Adobe tech note referred to above. It explains a little more about what is going on. Short answer is that you have to watch your free RAM and your Photoshop Efficiency rating together to find the right % allocation. Depends on how many other apps you have running and all that.

For the ultimate long answer on Photoshop RAM and a comments discussion try this Adobe engineer blog post (http://blogs.adobe.com/scottbyer/2006/03/reap_what_you_m.html).

[SloYerRoll]

Thanks CB.

Now I've read both articles and have a better undertanding of how memory is utilized and allocated.

From what I gleaned from the articles. This 75% static number is a default standerad percentage taht the average user will need to maxamize effencieny. I still didn't see anywhere in either link that said, "X is the reason you don't want to go over the 75%".

I think I'm jsut gonna start playing around w/ the percentage and run a few other high memory use java applications I have sitting in the archives.

I did find it very interesting when Russell Williams said: “Just to be a little more explicit on the “3+GB thing” — if you’ve got 4GB and are still hitting the scratch disk on either Mac or Win, you will probably see significant benefit from adding RAM. 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.


40% from 2GB!

[Richard]

40% from 2GB!

Easy, there, Jon. If you are not hitting the scratch disk, additional memory won't speed things up for you.

[SloYerRoll]

Easy, there, Jon. If you are not hitting the scratch disk, additional memory won't speed things up for you.I understand that Richard. I just thought it was interesting.

Cheers,
-Jon

[colourbox]

I did find it very interesting when Russell Williams said: “Just to be a little more explicit on the “3+GB thing” — if you’ve got 4GB and are still hitting the scratch disk on either Mac or Win, you will probably see significant benefit from adding RAM. 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.
40% from 2GB!

That was the part of that article I noticed too. It is the entire reason I bumped from 3GB to 7GB...and then stopped there. I think the 40% from 2GB speedup is simply because of thresholds. You added just enough for OS caching to make a difference, but once it makes a difference, it's a big difference. I would guess that adding another 2GB and another 2GB would result in rapidly diminishing returns.

I think I read another place that the "sweet spot" for Photoshop and big docs was 8GB RAM; you only add more if you have another app that needs it (virtual OSs?), or have too much money.

Good tip from Richard too. If someone only edits Photoshop files so small that they never need scratch (i.e., all graphics are only low-res for web sites), going above 3GB RAM would be a complete and total waste of money.

[HarlanBear]

Not to through a wrench into the works, but I’ve done some testing by adjusting the allocation of RAM for PSCS3 and then watching the efficiency monitor when working on large files or ones with many layers. As long as it stays at 100% you are not hitting the scratch disk, as Richard said. When it drops below 100% and therefore hitting the scratch disk, I then adjust the RAM up a little and leave it there. That way other apps are also operating at high efficiency and no effect to PS. Sort of like backing off sharpening, if you do that.

[kwcrow]

SloYerRoll,
I am not sure if you are on a mac or windows xp or what, but there is a setting in your boot.ini file in your root directory called "/3GB" that will allow ps3 to take up to 3gb of memory out of 4gb total. This will only reserve 1GB for your OS so you may run into a few more gliches if you have a 512mb video card or something, but I have used it and it really helps on big files. I do sports montages that have 20-30 layers and are 4000X6000 pixels.

This is what my boot.ini looks like.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional /3GB" /fastdetect /NoExecute=OptIn /3GB
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional /3GB" /fastdetect /NoExecute=OptIn /3GB

You can also bump your percentage up some with 4gb of memory above 75% and you should have enough for other programs. Windows XP can address 4GB of memory but without this setting can only give 2gb to each process. With this setting and percentage=100% I still only see PS using max of 2.5GB.

If you have more than 4GB of virtual memory you can also google on /PAE switch that supposedly can help also above 4gb.

-Kevin

[SloYerRoll]

SloYerRoll,
I am not sure if you are on a mac or windows xp or what, but there is a setting in your boot.ini file in your root directory called "/3GB" that will allow ps3 to take up to 3gb of memory out of 4gb total. This will only reserve 1GB for your OS so you may run into a few more gliches if you have a 512mb video card or something, but I have used it and it really helps on big files. I do sports montages that have 20-30 layers and are 4000X6000 pixels.

This is what my boot.ini looks like.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional /3GB" /fastdetect /NoExecute=OptIn /3GB
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional /3GB" /fastdetect /NoExecute=OptIn /3GB

You can also bump your percentage up some with 4gb of memory above 75% and you should have enough for other programs. Windows XP can address 4GB of memory but without this setting can only give 2gb to each process. With this setting and percentage=100% I still only see PS using max of 2.5GB.

If you have more than 4GB of virtual memory you can also google on /PAE switch that supposedly can help also above 4gb.

-Kevin

Hey Kevin,

Thanks for the info. I've seen quite a few posts about the /3GB switch. When I Googled "vista /3GB photoshop x86" all the forum posts and websites say that while they don't see the full 4GB they see ALLOT more that I'm seeing..

I also understand that the amount of RAM that Photoshop "sees" is relative to available RAM not total. But I'm only running 5 b/g process and NONE of them are RAM intensive (trillian/outlook/huey/sidebar/ff). So I'm only running about 750MB of RAM total and I then launch Photoshop and it only sees 1.7GB? Where's the other 1GB+ of RAM that Ps doesn't see?

Somethings not adding up. I know the math behind this is pretty heavy. But it's not even making sense from the high level view I'm seeing it at.

Any ideas?