Hmy memory is not being recognized correctly

[SRtiV2yqdCnR]

I have recently built a new system.

Windows 7 x64 Ultimate.
990 FX A-UD3, Motherboard
FX 4100 CPU
Asus EAH 5770, Graphics Card
OCZ Vertex 3 120GB Solid State Drive [as main drive]
Seagate 2TB 5900 Secondary Drive
Pioneer DVD Burner
Corsair Vengeance 4x4GB 1866Mhz DDR 3 Memory [CMZ8GX3M2A1866C9]
Which is on the Gigabyte Qualified Vendor List for my MB
Thermaltake 675 Watt Power Supply

The problem i have is that it is only recognizing the memory as 1333Mhz.
When i go into the bios and set the speed to anything else when i boot up a message appears saying that i have overclocked the system and reverts it back to 1333Mhz. If i only have 2 memory modules in it does not make any difference, it still sets itself to 1333Mhz. I have even swapped over the memory and tried my G Skill 4x2Gb 1600Mhz memory with the same result. i have even tried with just 2x2Gb memory modules and yep same result 1333Mhz. I have ran memtest86+ on all 8 memory modules with no errors, so can you please help me.
Thanking you in advance.

Regards
Walter S

 

[ShadyHamster]

i believe 1333mhz is the standard speed for this kind of memory, the 1866mhz is basically the overclocked rated speed, also i think its only available with intels xmp profile, with an amd system you will have to increase the ram voltage to get it stable.

feel free to correct me if im wrong.

 

[SRtiV2yqdCnR]

I have sorted it out, I inserted the modules in 1 and 3. Insead of having 16Gb i am running 8Gb and every thing is running flawlessly at 1866Mhz. Which means that the information that Gigabyte gave was wrong. You cannot use 4 Modules of 1866Mhz in the 990 FX A-UD3 Motherboard.

 

[Proximon]

It has very little to do with the motherboard. The memory controller resides on the CPU. I would like to see a bit more on this subject though...
Everything I found in the last 15 minutes indicates that what you are seeing is exactly as it should be. AMD certifies that Bulldozer can run two sticks of DDR 1866, one per channel. It also states that if the sticks are in the same channel, they are downclocked to 1600. So that would mean your max speed with 4 slots filled is APPARENTLY 1600.... but realistically I would expect 1333.

But again, I would like to see a better reference on this than I have found yet.