All 32-bit systems have a RAM limit of 3 GB. This limits the maximum amount of RAM a system running on a 32-bit Linux can support. So, even if you have more than 3 GB of ram installed, it will show only 3 GB.
There was a previous workaround which allowed us to use more than 3GB of ram in Linux by installing the server Kernel. This provided us with a kernel which had PAE enabled. This could also be done by recompiling the Linux kernel with PAE enabled. But, this is no longer possible now as the i386-server flavor of Linux is being dropped according to the Ubuntu Wiki.
Thankfully, instead many OEM’s have made a request for a 32-bit Ubuntu with PAE enabled. In response to this, Karmic Koala has options to use PAE. This has been possible due to the meta package
linux-generic-pae, which has been added to the Karmic Koala build and allows us to enable PAE for the desktop version.
To enable more than 3 GB, enter this in a terminal. This command will install the PAE packages.
sudo apt-get install linux-generic-pae
Now after restarting the sytem, your Ubuntu should use the full RAM resource of your computer.
For more information on PAE, see the Wikipedia page here.
For more information on meta packages, see the Ubuntu help page here.
[ Via Web Upd8 ]