mcclnx mcc wrote: > we plan to setup our ORACLE database server (32 bits DB) and use dell > r900 server. This server can put up to 128GB RAM. > > We are thinking use 32 bits CENTOS 4.7 or 5.2. My concern about > CENTOS 5.2 is it only support up to 16 GB RAM on 32 bits O.S. > > Any suggestion? To get beyond 4 GB of RAM with a 32-bit Intel CPU, you have to turn on PAE mode, which is a very ugly hack, invented several years ago now. It dates back to the old Pentium Pro! It was created before inexpensive 64-bit CPUs were available. Systems being built today should not use PAE mode, IMHO. If you need more than 4 GB of RAM today, use a 64-bit OS and applications. That will let you address the full memory capability of that server. In PAE mode, the system runs a little slower due to the extra overhead of the more complicated memory management scheme, and it can't really address that 16 GB all at once. It's kind of a like the old DOS days when we had 32-bit CPUs but could only address 64 KB of memory at a time, and could only access 640 KB without resorting to PAE-like hacks called EMS and XMS. These workarounds are best consigned to the dustbin of history.