Gigabyte X58A-UD3R RAM recognition issue

[Serunson]

Hello Daniweb yet again I have returned! This time with a rather weird issue...

My latest custom build PC has 6Gb of Corsair RAM, but my copy of Windows 7 Pro x64 says "6.00Gb (4.00Gb usable)"

Any ideas? I have gone through the internet to look for various solutions but no one seems to be able to provide a straight answer. Windows's Memory Test comes up with no errors what so ever, and in Task Manager it only reads there being a total of 4Gb as 'usable'. Any ideas why the other 2Gb decides not be used? Re-seating the RAM does work, but upon reboot it then decides to revert back to this message.

Any ideas anyone?

Serunson, out.

[Serunson]

In case anyone else gets this issue - resit your CPU, and enable Profile1 in the RAM settings in the BIOS. Has fixed mine after 5 reboots (touch wood).