Asus Z77 Sabertooth - DIMM slots A2 and B1 stopped working

[Slats]

Returned from work earlier this week and noticed my system was locked with red Mem OK light illuminated. I rebooted and got the overclocked failed so I default memory to 1333 and rebooted. I then rebooted again to check settings and upon entering the BIOS I noticed that BIOS was reporting 8 gigs of memory when I have 16 installed. I rebooted and entered windows to verify and sure enough on 8 gigs, although CPU-Z reports 16 gigs. I scoured the forums and noticed this is quite common on the Z77 platform across all models, both with Asus and other manufactures. I learned the most identified culprit are bent socket pins so removed my H100 cooler and processor and inspected with a flash light and large magnifying glass for some time but didn't find any pins that looked out of place. I have even taken some photographs so I could look a little closer while in a windows environment. This is very frustrating as I cannot utilize my 4x4 gig 1866 memory. Through a process of elimination I have confirmed all sticks of memory are good and all test good in memtest 1.5. If I place a single stick in either DIMM A2 or B1 (Middle 2 slots) the machine refuses to boot but any other combination works fine. I have not removed the board yet to determine if it could be grounding on something that could cause this as I wanted to get the forums opinion to see if others have experienced a grounding issue a year post build when I've never had any problems before.

Please feel free to share your thoughts on this. All recommendations and opinions are appreciated.


Thanks, Todd



Asus Z77 Sabertooth (BIOS 2104)
2500K@ 3700mhz
Corsair Obsidian 650D Case
Corsair HX 750 PSU
4x4 Crucial Ballistix Tracer 1866 XMP 1.5v
Asus 7970 Direct CU II
Samsung 830 SSD
2x BluRay drive
2x storage Mech Drives

[HiVizMan]

Hello there

Sorry to hear about the hassles you are having, quick couple of questions and a suggestion.

Have you moved or added any hardware to your system lately. Basically I am wanting to find out if what if anything has changed in the environment of your system.

Now for the suggestion. Could you test each of the memory sticks as per the Memtest86+ guide in my sig. Use the 5.2 version from the download page. Basically I would like to confirm what you have found out but using a more robust test than what you originally used if you do not mind. This will allow us to work out where the issue is located. Namely is it memory slots that have died or become damaged or memory sticks - plus we have the memory controller on the CPU that may be playing around.

[Slats]

Headed to work. I will test all stick by themselves this evening and reply with results. But no I have not added any new hardware.

[HiVizMan]

Cheers thanks mate, will check back later tonight to hear how it goes.

[Slats]

Sorry for the late reply but have been busy with work. Below is the latest....

I just got the board back from RMA and it continues to suffer the same issues. The problem/repair on the service shipping pack list under the FROM: section reads "PTSI_CHANNEL2". All dimm sticks run individually in each slot and is recognize as 4gb. The 2nd dimm from CPU will not recognize any ram if either of the remaining slots are populated but recognizes fine if it is the only one in the motherboard. This is really frustrating and am beginning to wonder if the service center even bothered to check the board with each dimm slot populated.

I would appreciate if other forum members could share some thoughts on this.

[Chino]

Have you tried using the stock heatsink and see if that slot still gives you trouble?

[Slats]

No I have not as the Corsair H100 is installed as it has always been. Do you have experience with this being an issue? If you do, it worth my time I suppose.

[Chino]

Well. Sometimes when installing a custom heatsink users often overtighten the screws or other mechanism which cost the motherboard to warp and the CPU not touching one or more pins. Not saying this is your case, but it's a possibility.

[Slats]

Just finished swapping out the H100 with the stock unused 2500k HSF with the same issues. The H100 has stops that allow you to only tighten it so it bottoms out on the mounting bracket to prevent that issue. Through trouble shooting and reading up on the issue I have found many of the Asus z77 series motherboards (varying models) that seem to experience this issue.

Thanks for you time Chino.

[Slats]

Update. I RMA'd the board but when it returned it had the same issues. Talk with customer support and they stated my ram Crucial Tracer Ballistix 1866 XMP wasn't supported as it wasn't on the QVL. I asked if it was tested with all 4 dim slots full and he couldn't answer. Against my better judgment I picked up some 1600mhz Corsair that was on the QVL and it still suffers the same issue. I borrowed a 2600K to verify it was my 2500k memory controller and it still suffers the same issue. I was really hoping to get some better support. I will try to call Asus tomorrow to see fi I can have the board replaced. I do not want to deal with this board again.