ESXi – Showing 8GB RAM only

Hi Guys – so I trying to configure my SuperMicro X7DBR server to run vmware esxi. I was able to install it with no problem at all except that it does not display all of my RAM’s. I have 16GB installed but esxi it’s only showing 8gig. Is there a bios setting that i need to set prior to installing esxi? My hardware again is a Supermicro X7DBR with 2 Intel Xeon 5130 @ 2GHz with 16GB of RAM and 1TB SATA disk.

Thanks.