Available Memory Limitation When 4 GB Installed for some Discontinued Intel® Server Boards
For general help with the 4 GB memory limitation, please check the Compatible Memory and Compatible Operating Systems (OS) for your server board or workstation board.
To test whether the board or the OS is the issue, check the reported memory in the BIOS. If the BIOS reports the memory correctly, consult your OS documentation for instructions on setting the OS to correctly report all memory.
If you came here from an Asus* FAQ page, please note that their article only applied to a single Intel® Server Board that was discontinued in 2008.