Unable to Use Complete RAM installed

[vishnuchats]

I'm unable to use the complete 16 GB RAM installed in my desktop PC.

My System Config :
> AMD Phenom -ii X6 processor
> ASUS M5 A88-V EVO Motherboard
>AMD RADEON HD 6970 Graphics card (2GB)
> 2 x 4gb ADATA ram and 1 x 8 GB Corsair Vengeance RAM.

Everything was working well earlier for about an year.
And one day It showed 16 gb installed ram but only 8 gb usable.
After getting many suggestion I updated my system to Windows 8.1. (Previously I was using Windows 7 Ultimate.)

Then it became worse only 4GB usable in the 16 GB installed. Again after taking many things I updated by BIOS, graphics card drivers etc. Even windows updates.

Now it shows 12 GB usable out of possible 16 GB..

Please Help Me in Using the complete RAM installed.. ( * note the whole 16 GB was working fine for nearly one year after assembling the system even though they are of different manufactures)

thanks in advance

 

[clayofthe757]

You may have shotty sticks, or just a dying stick. Remove all of the sticks but one and boot the machine. Repeat this with each stick. If it will not boot with one particular stick then you have identified the problem component. DDR can be fickle. It isn't really too popular a notion to mix manufacturers in one case either.

Good luck.