I was finishing an hour long sequence today and I noticed that Premiere CS5 was using 18GB!

Anyone else experience this?

How much RAM do you have? Memory is both dynamically and manually configurable in the CS5 suite. By default it will reserve 75% of available RAM for the core Adobe programs that need lots of RAM (PPro, AE, AME, and Encore), leaving 25% for other apps. If a single CS5 app is running (eg PPro), it gets the whole allocation to itself. If you have 24GB of RAM on your system, PPro would "own" 18GB of it. You can adjust these settings in the Preferences dialog. Does that explain what you're seeing or is something else likely going on?

Thanks Pete. You said exactly what is happening - I have 24GB and PPro was the only Adobe app open.

My guess is that Premiere was storing the frames that I played in ram for quick playback. Because the sequence is an hour long, there were quite a few frames that I scrubbed through.

Steve,or anyone that knows, in CS3 and my RT.X2 it takes my second monitor and divides it up into my clip choices on the left side of the second monitor and the recorded clip on the right side of the second monitor. It is wonderful to be able to view everything so large while making my editing choices.
I am planning on purchasing CS5 without a Matrox RT.X2 card and am wondering if I am going to have to give up this wonderful editing workflow.
Any ideas or questions appreciated.

I am using CS5 and a MX02 so far it's not bad - drivers were released about 3 weeks ago, you will have to edit in a matrox preset. I have had a few crashes bugs etc but the HDMI output feeding a 42 inch HDTV works great. Not sure how much Rt.X2 is supported or if this type of split screen output is supported.