Dual Channel Ram Only Has One DIMM Usable?

[lotuseater]

Does dual channel ram always have only one of the Dimms as usable in Windows?

I have the following setup:
Asus Sabertooth 55i
I5-760
G.Skill F3-12800CL9D-4GBRL DDR3-1600 2048MBx2

I installed this dual channel ram as recommended in my Asus manual in slots A1 & B1. I have updated to the latest bios (1807) with default settings, then enabled XMP. The bios system information shows system memory usable size: 2046MB.

In Windows, it shows 4GB installed but only 2GB usable. As seen in the screenshots below.

If I install both dimms in slots B1 & B2 the bios shows 4096MB available, windows shows 4096 usable, and CPU-Z shows 4096 single.

Is my Ram working properly having only half of it as usable?

[lotuseater]

I found the following two lines in my motherboard manual

- Due to Intel spec definition, X.M.P. DIMMs and DDR3-1600 are supported for one DIMM per channel only.

- According to Intel spec definition, DDR3-1600 is supported for one DIMM per channel only. ASUS exclusively provides two DDR3-1600 DIMM support for each memory channel.


Is this why I am not able to use my ram on channel A?
Do I need to downgrade to DDR3-1333?

[leeghoofd]

A1 , B1 should be correct, if you do B1, B2 it's always single channel...

I got no clue why so many users here load XMP profiles. Just use the ram divider till you see 1600mhz, then verify the timings ( CL, TRCD, TRP and TRAS in your case 9-9-9-24 ) and set the required Dram voltage. WMP profilesa re not always 100% working, this due to bad SPD programming or issues with the boards bios to read them out.

I would test first with one dimm in slot A1 o r B1, test it thoroughly with Memtest. if it passes replace the dimm with the other dimm and test again. Then test the other slot 1. It might be one dimm slot is damaged.

If it will post but not stable, up the QPI voltage a bit...

[lotuseater]

Both dimms seem to work properly when installed in B1,B2 for single channel operation.

If I put either dimm by itself in slot A1, the computer will not post and boot.

I will try again in slots A1, B1 with your settings this afternoon. And also try one stick at a time in B1,B2 and run memtest in windows.

[lotuseater]

I got no clue why so many users here load XMP profiles. Just use the ram divider till you see 1600mhz, then verify the timings ( CL, TRCD, TRP and TRAS in your case 9-9-9-24 ) and set the required Dram voltage. .

My default timings show 9-9-9-24.
I do not see where to adjust the ram divider and check for 1600mhz? Is there another name for it?

[leeghoofd]

That will be Dram frequency in the AI tweaker menu (might have to set AI overclock Tuner to Manual mode to get access)

[lotuseater]

My dram frequency is currently set to auto and showing 1333 at the top for target ram frequency. I just got off the phone with Asus and they recommended changing the frequency to 800. (1600 is not an option for me)

I will try this when I get home today.

[droogie]

Good luck~

Let me know what you find out... Hopefully I can get it working on my end also.

[lotuseater]

Still having the same results. Not working.....

[lotuseater]

Newegg has offered me a refund for my motherboard. I am going to return it.

Should this setup be plug and play for dual channel operation?

Asus Sabertooth 55i
I5-760
G.Skill F3-12800CL9D-4GBRL DDR3-1600 2048MBx2


If so, I will just buy another new Sabertooth 55i unless there is a better motherboard in this price range.
This is what scares me from the motherboard manual:
- Due to Intel spec definition, X.M.P. DIMMs and DDR3-1600 are supported for one DIMM per channel only.
- According to Intel spec definition, DDR3-1600 is supported for one DIMM per channel only. ASUS exclusively provides two DDR3-1600 DIMM support for each memory channel.

[lotuseater]

Should this setup be plug and play for dual channel operation?

Asus Sabertooth 55i
I5-760
G.Skill F3-12800CL9D-4GBRL DDR3-1600 2048MBx2

Would I be better off going with the P7P55D-E Pro for any reason when replacing this motherboard?

[GSKILL TECH]

This memory is not plug and play, but after you enable XMP, it should basically be plug and play.

Based on what you stated, I believe your original motherboard just had a bad slot.

You can try a new saber, or get the P7P55. Either way, make sure the memory is firmly inserted, enable XMP, and you should be good to go.

Thank you
GSKILL TECH