Hi, I have an EVGA x58 132-BL-E758-A1 up until now I have been using 6GB (Triple Channel) Corsair Dominator 1600mhz 8-8-8-24 and the motherboard is detecting all of them in their respective slots. A week or so ago some Geil Dragon 16GB (Dual Channel) 1600mhz 11-11-11-28 went on sale so I decided to get it because it was so cheap.
So I put in the new RAM and notice that it is only detecting 8GB, so I double checked that they were in the correct RAM slots for dual channel and still nothing, Tried them in a number of different combinations, only 8gb showed up. Tried them both one at a time and they worked fine. I took the RAM around a friends house and it worked straight away on his, the full 16GB was shown in the BIOS and in Windows (He is using a Dual Channel motherboard). So I get home and put the RAM back into my motherboard to see if it was just me being an idiot and sure enough both sticks were being detected in Windows and the BIOS, even though I put them in the same slots with the same settings as before.
That was all a couple of weeks ago now and up until today all 16GB has been usable and been detected in the BIOS and in Windows. I turned my pc on this morning and now it is only showing 8GB in the BIOS and in Windows. I have tried multiple reboots and it is still only detecting 8GB.
 
I have changed nothing to make it stop being detected and the LED's that are on the RAM modules are glowing their normal colour. Also a wierd thing is that in CPU-Z it is detecting all 16gb, here is a screenshot of CPU-Z  http://i.imgur.com/YllIbtR.png  and here is a screenshot of Windows  http://i.imgur.com/xW9fumx.png
 
The only thing I can think to try is updating my motherboards BIOS but surely as they have been working for a couple of weeks now that can't help anything?
Any suggestions? 
p.s. Sorry about the wall of text
p.s.s System Specs:
Windows 7 Professional 64-bit
Core i7 920 @ stock
EVGA x58 132-BL-E758-A1
16GB Geil Dragon
EVGA GTX 470 x2 in SLi
Corsair HX1000
various hard drives
 

rjohnson11 

If it is showing 8GB in the BIOs then there is a problem. Try this old troubleshooting list of mine 

http://forums.evga.com/fb.ashx?m=479626 

 

 
I tried all of the suggestions in that thread and it still will only show 8GB in BIOS and Windows with CPU-Z still detecting 16GB.
 
I was reading around and apparently people that have a similar problem are attempting to increase the CPU VTT Voltage, although in all of their cases the motherboards they are using show the values in V and my motherboard shows the value in mV so what is a safe mV to go to to see if increasing this helps?
 
When I leave it on auto it shows that it is at +200mV

 
Have you tried a CMOS reset?

XrayMan

 
Have you tried a CMOS reset?

Yes I have done multiple CMOS resets and it is still the same.

I tried +200mv and +250mv and it still did the same.

rjohnson11

So if you try one stick at a time this works is that correct?

Yes each stick works by itself and i put my 6GB Corsair kit back in to test all of the RAM slots at the same time and it showed all 6GB so it isnt the actual RAM slots.

 
Try setting the Ram in the Bios manually to their default specs, and see if that works.

I have heard of some ram that is stubborn but I still managed to make it work. You'll have to try another ram and see if the problem goes away. You have six slots for ram in that motherboard. How many are occupied when you install  the ram...three slots?

You really need three modules otherwise you're running in dual channel mode which limits your memory bandwidth.

I tried the module that would not work in my motherboard on my friends and he said that it booted straight away, shows in his BIOS and also shows in Windows. It must be one setting that is causing it not to work as every RAM Slot on my motherboard works with other RAM.

ronnieb555

I tried the module that would not work in my motherboard on my friends and he said that it booted straight away, shows in his BIOS and also shows in Windows. It must be one setting that is causing it not to work as every RAM Slot on my motherboard works with other RAM.

If you're only using two 8GB memory modules, they should be installed as noted:
 

RAM Problem on X58 SLI LE - Post #8