ASUS Z270-AR: DIMM Slots B1+B2 Nonfunctional after CPU cooler upgrade

Samwise

n00b
Joined
Jan 3, 2013
Messages
8
Hi all,

I have a bit of a problem with my motherboard's DIMM slots that I'm hoping you can help me get to the bottom of.

I recently installed a new CPU cooler (Noctua NH-D9L). Since installing it, DIMM slots B1 and B2 on my motherboard (ASUS Z270-AR) are causing POST failures. The system boots up fine as long as B1 and B2 are empty.

Tested all four of my RAM sticks (8GB Corsair LPX DDR4 3000) in A1+A2 slots and they all work fine.

When A1, A2, and B1 are filled, the POST State LEDs show CPU (red), followed by DRAM (green). When all four slots are filled, only DRAM (green) lights up.

During POST, I hit the MemOK! button on the motherboard. It ran through its tests and rebooted a few times, but still didn't successfully boot.

I've taken everything apart, re-seated all the components, and applied some air duster to the DIMM slots, CPU socket, and the underside of the CPU, suspecting some kind of contact issue. I even went as far as to carefully clean the DIMM slots and the underside of the motherboard with a toothbrush and a touch of isopropyl alcohol. No luck.

I'm worried I might have accidentally damaged something while installing the new cooler, but I could not see any damage to the CPU socket, nor the CPU itself, upon close inspection. The only other possible cause I can think of is the old backplate, which required a bit of force to remove from the underside of the board.

The CPU is an an Intel i7 7700K, in case that helps.

What do you think? Is my motherboard busted?

Cheers!
 

x509

2[H]4U
Joined
Sep 20, 2009
Messages
2,630
Hi all,

I have a bit of a problem with my motherboard's DIMM slots that I'm hoping you can help me get to the bottom of.

I recently installed a new CPU cooler (Noctua NH-D9L). Since installing it, DIMM slots B1 and B2 on my motherboard (ASUS Z270-AR) are causing POST failures. The system boots up fine as long as B1 and B2 are empty.

Tested all four of my RAM sticks (8GB Corsair LPX DDR4 3000) in A1+A2 slots and they all work fine.

When A1, A2, and B1 are filled, the POST State LEDs show CPU (red), followed by DRAM (green). When all four slots are filled, only DRAM (green) lights up.

During POST, I hit the MemOK! button on the motherboard. It ran through its tests and rebooted a few times, but still didn't successfully boot.

I've taken everything apart, re-seated all the components, and applied some air duster to the DIMM slots, CPU socket, and the underside of the CPU, suspecting some kind of contact issue. I even went as far as to carefully clean the DIMM slots and the underside of the motherboard with a toothbrush and a touch of isopropyl alcohol. No luck.

I'm worried I might have accidentally damaged something while installing the new cooler, but I could not see any damage to the CPU socket, nor the CPU itself, upon close inspection. The only other possible cause I can think of is the old backplate, which required a bit of force to remove from the underside of the board.

The CPU is an an Intel i7 7700K, in case that helps.

What do you think? Is my motherboard busted?

Cheers!
Pure speculation here. When you were putting on the new cooler and tightening down on the mounting screws, you somehow applied a twist to the CPU, which maybe bent some pins? Have you removed the CPU and inspected the pins? Again, pure speculation here.
 

Samwise

n00b
Joined
Jan 3, 2013
Messages
8
Pure speculation here. When you were putting on the new cooler and tightening down on the mounting screws, you somehow applied a twist to the CPU, which maybe bent some pins? Have you removed the CPU and inspected the pins? Again, pure speculation here.

Possibly. However, when mounting the cooler, I was mindful to alternate between the screws to apply even pressure all across. I also made sure not to overtighten it.

I went ahead and checked the pins again and took pictures this time (attached). Hopefully that helps.

The pins looks fine as far as I can tell, but maybe I don't have a good eye for this kind of thing.

Should I try installing the CPU without that plastic cradle (see pic)?
Edit: Went ahead and tried that - no difference. System is running great as long as the two DIMMs are empty.
 

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viivo

[H]ard|Gawd
Joined
Sep 7, 2005
Messages
1,695
It's hard to tell from that picture. You should grab a bright light and look at the socket from all angles - any bent pins will stand out.

Also do the same to the CPU. I had a similar problem where a small, almost imperceptible amount of thermal paste made its way onto a few of the contacts. It won't hurt it to clean it with alcohol (preferably 91% or better) and a cotton swab or microfiber cloth.
 
Last edited:

capt_cope

Gawd
Joined
Apr 12, 2009
Messages
947
I would check the mounting on your cooler - it might be too tight. I had a similar problem the first time I delidded my 7700k - the height of the IHS was just a bit too high, after re-attaching the IHS (I put more pressure on it when gluing it down) all dimm slots worked fine.
 

Samwise

n00b
Joined
Jan 3, 2013
Messages
8
Thanks for the advice, all.

I just took it apart again and inspected the CPU contacts once more while shining a bright light into the socket. Again, I couldn't see any pins out of alignment - if there are any bent pins, they're inperceivable to the naked eye. As far as I could tell, the tips of all the pins were equal distance from one another.

I gently ran a toothbrush through the pins and blasted it with air duster. I also scrubbed all the contacts on the CPU itself with 91% alcohol and a cotton tip, then hit it with some air duster too. I applied minimal tightening on the cooler. As usual, it would boot up fine when using the A slots only. B slots still cause POST failure when occupied.

At this point, I'm about ready to cut my losses. Frustrating. :(

What I haven't tried is using alcohol to clean the socket/pins - I've only used air duster and a dry brush on that. So maybe I'll give that a go later on.

By the way, I am very happy with the cooler itself. It's so much more space efficient than my old liquid cooler, and performs just as well, if not a little better temperature-wise. Less hassle to install too. These Noctua coolers seem pretty nice.

Thanks again - If I do solve the issue, I'll report back.

Edit: Maybe I should de-lid the chip and reapply it? I'm just a little hesitant on that, since delidding is complete unknown territory for me.
 
Last edited:

capt_cope

Gawd
Joined
Apr 12, 2009
Messages
947
Thanks for the advice, all.

I just took it apart again and inspected the CPU contacts once more while shining a bright light into the socket. Again, I couldn't see any pins out of alignment - if there are any bent pins, they're inperceivable to the naked eye. As far as I could tell, the tips of all the pins were equal distance from one another.

I gently ran a toothbrush through the pins and blasted it with air duster. I also scrubbed all the contacts on the CPU itself with 91% alcohol and a cotton tip, then hit it with some air duster too. I applied minimal tightening on the cooler. As usual, it would boot up fine when using the A slots only. B slots still cause POST failure when occupied.

At this point, I'm about ready to cut my losses. Frustrating. :(

What I haven't tried is using alcohol to clean the socket/pins - I've only used air duster and a dry brush on that. So maybe I'll give that a go later on.

By the way, I am very happy with the cooler itself. It's so much more space efficient than my old liquid cooler, and performs just as well, if not a little better temperature-wise. Less hassle to install too. These Noctua coolers seem pretty nice.

Thanks again - If I do solve the issue, I'll report back.

Edit: Maybe I should de-lid the chip and reapply it? I'm just a little hesitant on that, since delidding is complete unknown territory for me.
If you haven't already delidded your cpu I doubt doing it will fix this.
 

ManofGod

[H]F Junkie
Joined
Oct 4, 2007
Messages
12,647
If you haven't already delidded your cpu I doubt doing it will fix this.

Yeah, at this point, the OP has a bad stick of ram, bad mainboard or bad cpu, unfortunately. Hey OP, try increasing the DRAM voltage a bit, from 1.2 to 1.3v, and see if that helps. A few years ago, I had a 6700k with a memory controller that did not work well at the proper 1.2v of the ram I was using. I had to increase it to 1.3v at stock settings, which was not good at all. I had to RMA the cpu to get it fixed.
 

hititnquitit

[H]ard|Gawd
Joined
Apr 16, 2018
Messages
1,716
Have you checked the back of the mb where the cpu socket is located? You may have a short somewhere under the new back plate.
 
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