PS RAM question

**jpacer** · December 27th, 2009, 11:27 PM

Ok, I have what may be a stupid question, but I've googled around and couldn't find an answer to this, so I figured I'd ask here.

First off, here's my general system specs:

Pentium D CPU 2.80 GHz, 2.79 GHz
3.50 GB RAM
Windows XP 32-Bit
Photoshop 7.0

Anyway, I used to have just 1 GB RAM, but for XMas upgraded to 4GB (2x2GB RAM cards/sticks/whatever they might be called). Now, I know all about the problem with 32-Bit OS's which is why my RAM's capped at 3.5, so that's not what my question is about.

My question is, when running Photoshop and going into the memory usage settings in Preferences it says that 1777 MB of RAM is available. So, that's almost 2 GB. Why is the other 1.5 GB I supposedly have access to not available in Photoshop?

Actually, since I'm here I might as well ask another question. I upgraded the RAM with the intention of eventually getting a 64-Bit OS which would give me access to more RAM, and then upgrading PS to CS4. Is that even worth it, or should I just wait until I can afford a whole new rig? I ask, because I read conflicting things online as to whether or not the Pentium D CPU and chipset is even true 64-Bit and might be slowed down by a 64-Bit OS.

Thanks for any insight.

**Huey Yeng** · December 28th, 2009, 02:15 AM

I'm running PS CS4 64-bit on my desktop which has similar specs like yours (Pentium D 2.66GHz with 2GB of RAM instead with Win7 RC1 64-bit as the OS). So far I don't encounter any slowdown while painting in PS.

As far as I can remember from the PS documentation, Windows only allocate a max of 1.7GB of RAM if not mistaken on a 32-bit environment. A max of 3.2 GB is allocated on a 64-bit environment if still using CS4 32-bit.

For CS4 64-bit on 64-bit Windows XP/Vista/7, it should use as much RAM as possible on today's system limit. In theory if you have 8GB of RAM, you could use up 7GB out of 8GB of RAM for PS.

Hope that helps.

**jpacer** · December 28th, 2009, 11:04 AM

That does help a lot. That clears some things up. I couldn't find that in my documentation, but it sounds good, so I'll take it.

I'm also glad to hear that you're running Win 7 64-bit and CS4 with no problems on that system. That makes me feel like I can still get a couple good years out of my machine!

**redcloud02** · January 1st, 2010, 07:51 AM

Definitely go 64 bit windows. I did, worried that a lot of my programs wouldn't run properly, but every single program of mine runs fine. I'm getting Windows 7 on my main PC soon so I'll be able to get 8GB of RAM finally and let Photoshop use more than 1.5 GB. I forsee a huge jump in performance.

**FactorZero** · January 3rd, 2010, 12:11 AM

From what i've read about 32 bit OS' is that they only allow a max of 2GB to be allocated to a single program. So even though your system has 3.5GB XP won't put more than 2 into PS. Also under edit>preferences>performance there should be a slider that allows you to change the amount of RAM PS uses. I think it's set to 50-60% by default.

**Zirngibism** · January 3rd, 2010, 09:48 PM

Yes, and under the same performance/file handling menu, you can free up RAM by bring down the level of undos you have, and by lowering the cache menus.

Oh, and when you slide up PS's memory allocation, don't make it higher than 85% (and you're safer with 80%) because it could make your whole system crash.