转自http://www.jonboy60.com/2011/01/20/howto-install-kernel-pae/

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The Linux kernel with support for up to 64GB of high memory. It requires a CPU with Physical Address Extensions (PAE). Physical Address Extension (PAE) is a feature to allow x86 processors to access a physical address space (including random access memory and memory mapped devices) larger than 4 gigabytes. The non-PAE kernel can only address up to 4GB of memory. Install the kernel-PAE package if your machine has more than 4GB of memory.

Do your computer had more than 4GB RAM? Did you upgrade your computer to a 4 GB or more RAM? Do you have a 32bit system? If yes, then your machine may not show up total 4Go, in this case you Linux need to use the Linux kernel compiled for PAE capable machines. The PAE package includes a version of the Linux kernel with support for up to 64GB of high memory. It requires a CPU with Physical Address Extensions (PAE).

Checking Processor
$ cat /proc/cpuinfo | grep -i PAE
(If you see pae, then your processor supports PAE)

Installing PAE in Fedora/RHEL/CentOS
For fedora /RHEL and CentOS open terminal and Run the following command :
$ yum install kernel-PAE

Then
Reboot

Now PAE kernel should be booted as the default option in the GRUB boot menu.

Installing PAE in Ubuntu
If you had more memory before to install Ubuntu 10.04 and above then you don`t need to do anything since ubuntu automatically installs the PAE enabled kernel if it detects more than 3 Gb of available memory. In the case of the liveCD, a working network connection is required, since the PAE enabled kernel packages are not present on the CD.

If you have Ubuntu 10.10 already installed and you just upgraded your Ram to 3GB or more, then you need to install PAE kernel. To do that open terminal and type the following command :
$ sudo aptitude install linux-generic-pae linux-headers-generic-pae

Then
Reboot

Now PAE kernel should be booted as the default option in the GRUB boot menu.