Activity Monitor shows 2GB instead of 4GB RAM

[samex]

Hello i have a problem,

in the systemprofiler its show me that I have 4GB Ram installed. But in the Activity Monitor it´s says that I have only 4GB RAM and the Command "top" in the Terminal show that I have 2GB too.

 

What can I make to change that issue??

 

EDIT : On Bootloader its show me also only 2GB RAM ( Chameleon RC5)

EDIT : FIXED IT WAS A BIOS SETTING, THANKS

 

SameX