486 vs 686 pae(Physical Address Extension)

The i486 version should boot on all computers (486 and higher), but is limited to accessing less than 4 GB of RAM. The i686-pae version works on Intel/AMD 686 and higher computers and includes a Physical Address Extension to permit accessing more than 4 GB of RAM. This version also supports the use of multiple CPU cores.

http://gparted-forum.surf4.info/viewtopic.php?id=16998