16GB RAM installed in ASUS P7P55D-E LX but only 8 GB usable

[Deshawn]

so this is the case I have this 2x2gb Mushkin Ridgeback DDR3-1600 CL6 but now I have upgraded my machine to 4x4gb Corsair Vengeance 1600 MHz CL9 but now my machine is using just the 8 GB and the windows 7 ultimate 64bit showing the 16 GB and only 8 GB out of it usable . I did very thing that I can possibly do but nothing is working. I even updated my bios but still I have the same issue . I have even changed the normal"-clocking to x.m.p inside the bios but still no avail . I checked the corsair web page and there in the FQA it say the ASUS P7P55D-E LX is compatible with the ASUS P7P55D-E LX so why is this issue . can anyone here help me on this I would be really appreciating this .

thanks

[Jhonny.Bravo]

That is really very much frustrating , I have the same problem with my Gigabyte Motherboard . well when I checked closely I found out that I have not inserted one of the Modules fully . so I suggest that you first check that , see if they have sited fully into the MOBO or just reseat again .

[Kabilan]

Looks to me it a bad stick of RAM or may be the Motherboard has been defective. In case in case you need to know that I suggest that you try all the ram in good slot,, then pair them up . with the pair try in both pare of slots. You will know if either a bad stick or one (or pair) of slots that are bad. And the main thing , just check the Ram voltage/timings.

[Oviyam]

Need help on the same issue with my PC with windows 7 it is showing that Installed memory (RAM) 16,0 GB and the 8,00 GB usable. Can anyone explain what is happening here . I just updated the BIOS a few time ago and looking if any other update is available. Please help

[Mayuus]

The RAM require to be correctly seated Look at the Resource Monitor if the Hardware Reserved 8000MB after that the BIOS is shutting down 2 of the 4 sticks. usually this is a DRAM and/or QPI/VTT Voltage issue.