32 bit system with PAE

The fundamental difference between 32 and 64 bit systems is the size of
memory addresses. In theory, a 32 bit system can not work with more than
4 GB of RAM (2³² bytes). In practice, it is possible to work around this limitation by using the 686-pae
kernel variant, so long as the processor handles the PAE (Physical
Address Extension) functionality. Using it does have a notable influence
on system performance, however. This is why it is useful to use the 64
bit mode on a server with a large amount of RAM.