Make Ubuntu Faster: Address The Maximum Amount of RAM Under Ubuntu

You don't need a 64-bit Linux Kernel to address more than 3.5 GB of RAM.  Here's how you can address nearly all of the 64GB possible using PAE.  Ubuntu ships with a non-PAE kernel by default.  This means that any computer with more than 3.5 GB of RAM, some of the RAM goes unused because the address space for that RAM is being used by other system resources.  You can see this effect when you click System->Administration->System Monitor and look at the little red pie-chart for Memory.  Your usage should be "of 3.9GiB" when you have 4GB of RAM.  If you have any more than 3.5GB (up to 63 GB of RAM or so), then you should see it there.  Here's how to enable PAE and get more RAM if it doesn't.

1. Open Synaptic Package Manager
2. Remove all linux-image and linux-headers packages, except the one that would automatically remove a driver such as the nVidia Driver.
3. Add linux-image-generic-pae and linux-headers-generic-pae

Reboot and cross your fingers!