On my older system i ran the 32 bit version of Ubuntu with 4 GB of ram and noticed it rarely come near 1 gig of usage.I have my new system running with the 64 bit version.The new system is a quad core with 8 GB of ram and Ubuntu is using 1 gig now.Is this normal?I have run top and noticed certain processes such as compiz,xorg and lightdm seeming to be using a lot.I also upgraded in my new system with an msi radeon hd6450 graphics card that s supposed to have 2 gigs on it.
First, 64 bit executables tend to be larger than 32 bit executables, which could mean more RAM usage. Though I doubt this would be really noticeable.
Second, you want for Ubuntu to use your computer's RAM. The fact that you have 4GB more RAM installed means that Ubuntu will use RAM more eagerly. And that is a good thing.
To put your experience in relation: On this very machine, I have 4GB of RAM of which 3GB are currently in use. Even though some programs eat memory as if it was candy (e.g. Java), not using the available RAM would be bad for performance. You always want for working data to be in the RAM and not on your slow HDD.
So having 1GB in use means your system is pretty much lazy and working normal. Which isn't to say that it wasn't normal for your system to eat up 7GB. Normal depends on the software you run.
On the requirement page for Ubuntu 12.04, it says 512MB are needed if you want a desktop environment. 384MB are needed for installation without it.
Those requirement limit what a PC needs to run Ubuntu. Any more RAM is bonus and should be used for performance's sake.
One thing that I have noticed contribute massively to RAM usage is resolution size, and colour depth. Using 16-bit colours over 32-bit, and using 1024x768 over 1200x900 [or whatever massive] resolution can save 50MB and upwards, depending on your current settings.
However, this should only be done if you want to minimize the RAM and amount of processing done.