6GB RAM, 4GB usable

[chickenroyal]

Hi guys,

Noticed last night that Windows 7 (x64 Ultimate) says I have 6GB RAM, but only 4GB is usable. Not sure why it's saying this now, because it used to say all 6GB was available. CPU-Z is saying "Size: 6144MBytes" and "Channels #: Triple".

Posting this thread in general hardware because after some googling, I've found that it could be a number of reasons. Either a faulty RAM stick, mobo needing a BIOS update (GA-X58A-UD3R) or bent CPU pin on mobo. But as it was previously recognising all 6GB, I'm not sure what to try first.

Any ideas and help would be greatly appreciated.

PC specs:
Gigabyte GA-X58A-UD3R Intel X58 Socket 1366 (F3 BIOS)
Intel i7 920 2.66GHz 8MB Cache Socket 1366
Corsair XMS3 6GB (3x2GB) DDR3 PC3-12800C9 (1600MHz) 1.65V
XFX ATI Radeon HD 5870 1024MB DDR5 PCI-Express
Corsair 750W TX Series
Windows 7 x64 Ultimate

 

[chickenroyal]

Showing 4GB during POST at boot and in BIOS. I'll test each RAM stick individually.

Got nothing overclocked, was thinking about doing that sometime soon - guess it'll have to wait a bit longer!

Thanks for the help so far.

 

[chickenroyal]

Tested each stick individually, one of them is faulty. Bought them in April from OCUK, so should be a case of RMA them? As this was my first build, never RMA'd something before. Do I get in touch with OCUK or Corsair?

Thanks again for the help, very much appreciated.