I have a server with 2 3ghz xeon's that are x86 cpu's and I have 4GB installed.

The bios reports all 4096MB.

Windows Server 2008 had PAE disabled from which I saw 3326MB.

Enabled PAE via Bcdedit /set PAE forceenable.

Physical Address Extension (PAE)
Supported by Operating System Yes
Supported by CPU Yes
Active Yes

Physical Memory
Total 3326 MB
Used 930 MB
Free 2397 MB
Utilization 28 %