8G Ram installed but 4G usable

[geossl]

Dear All,
 
  My motherboard is P55A-UD3. There are 4x2G RAM.

  However, the bios reports all 4 modules of RAM but 2 dimm channels are disabled. Win7 (64bit) reports 8G RAM (4G Usable).

  How to fix this.

  I already loaded the latest BIOS.

[Dark Mantis]

Hi and welcome.

I would think that it is quite possible that this is down to a bent pin or pins on the CPU socket. Have you had any BSODs recently ? Also what voltages etc are you using at the moment ?

[Lsdmeasap]

What voltages do you have set?   Can you please test with three sticks and see if you get 6GB?  Two sticks will always need to be in the white slots, but if you do get 6GB with 3 sticks, then test the other slot with that third stick to, this way you know all the slots are OK and no bent CPU socket pins.

Then if that is all OK, it's probably just voltages need adjusted, maybe ram voltage increased a little more than spec, or QPI/Vtt may need adjusted to 1.2-1.4+ depending on your CPU

[geossl]

Manual said it cannot use 3 modules , so I just test with 2 modules in all combination of 4G.
It seems that all four ram modules is working.

Besides, I am using default voltage. I did not overclock. Is this related to voltage?

Hi and welcome.

I would think that it is quite possible that this is down to a bent pin or pins on the CPU socket. Have you had any BSODs recently ? Also what voltages etc are you using at the moment ?

[Dark Mantis]

Well it is quite possible that you will need to increase the voltage a little to compensate for filling all the slots and putting an exttra loading onto the memory controller. If your default voltage for these sticks is 1.5v then try increasing it to 1.55v. If the default is 1.65v then up it to 1.68v -1.70v. Just m,ake sure that you maintain the 0.5v max differential between the QPI/Vtt and the DRAM voltage.

[Lsdmeasap]

I was trying to get you to test the slots really, not the memory itself.   You can use 6GB / 3 modules if you want, please test as I mentioned previously, thanks!

As for voltage you may need to increase the QPI/Vtt voltage, the ram voltage should be fine at it's stock spec'd value.   You need to do the test I mentioned above before anything else though, so you can see if you have bent CPU socket pins.   Or you can remove the CPU and look if you want, if you do that please take several images for us to look at.  Do this in a well lit room with no flash, and the camera set to macro mode if it has that option.  Take the images from several angles off to the side looking into the CPU socket, just not directly over it. 

And be VERY Careful while there is no CPU in the socket!!!

[Dark Mantis]

And be VERY Careful while there is no CPU in the socket!!!

You wouldn't be the first person to put the camera lens down onto the socket and bend some pins whilst at it! 

[Lsdmeasap]

Any updates on this?  Just checking in!

[geossl]

I cannot get it with 6G.

With the white slots is filled, I try all combination but cannot achieve 6G.

Only Channel 1 and 2 can be enabled.

I also took out the CPU but cannot find any pin bent as the pin is so close and small, it is packed so dense together.

Any updates on this?  Just checking in!

[Dark Mantis]

I also took out the CPU but cannot find any pin bent as the pin is so close and small, it is packed so dense together.

That was precisely why Lsmeasap and I asked you to take photographs of the socket. We are used to seeing these pin configurations and spotting anything out of the normal.

[JFC15]

I had this same problem... this is what worked for me...

Check the system configuration settings
 This problem may occur because the Maximum memory option is selected incorrectly. To fix this, follow these steps:

1. Click Start, type msconfig in the Search programs and files box, and then click msconfig in the Programs list.
2. In the System Configuration window, click Advanced options on the Boot tab.
3. Click to clear the Maximum memory check box, and then click OK.
4. Restart the computer.
 

[Dark Mantis]

I had this same problem... this is what worked for me...

Check the system configuration settings
 This problem may occur because the Maximum memory option is selected incorrectly. To fix this, follow these steps:

1. Click Start, type msconfig in the Search programs and files box, and then click msconfig in the Programs list.
2. In the System Configuration window, click Advanced options on the Boot tab.
3. Click to clear the Maximum memory check box, and then click OK.
4. Restart the computer.
 

That is another point that is quite possibly the issue. As JFC15 has just said it is worth checking out. Here is the shortened version for you:

Start/run/msconfig/boot/advanced options/maximum memory

[geossl]

CPU PHoto....

[geossl]

Socket Photo

[geossl]

I have also tried to configure with Start/run/msconfig/boot/advanced options/maximum memory , unchecking the maximum memory.

However, is does not work.