I recently decided to upgrade ubuntu 10.04 to 12.04. My old MV Mobeus was already dual-booting the desktop and server versions of Ubuntu from the GRUB boot loader.
I managed to upgrade the desktop version from 10.04 to 12.04 easily, and without any problems, but since I'd already hashed up my server installation, I decided to reinstall the server.
I was soon told by the installer that my processor didn't have 'pae' (physical address extension), but leaves me to question whether or not there are significant kernel differences between desktop and server.
By the way, the processor is the Intel Pentium M 1.6Ghz, with Intel SpeedStep Technology.