Question Single channel RAM works, dual channel doesn't on new build

Aug 12, 2019
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I've just upgraded from a 6 year old PC I built to a new one. B450 Carbon motherboard with a 3700x and GTX 1070.

I had a bunch of issues which came down to the BIOS needing updated which I did. After this, the EZ Debug LED would get stuck on DRAM and not go past.

So running dual channel, I can't get past POST. I removed 1 stick of RAM and it works fine (I'm using it now), but of course I'll have only single channel and 1 useless RAM stick on my desk.
I'm using the Corsair Vengeance LPX DDR4 3200 MHz C16 XMP 2.0 RAM kit (2x16GB) - bought new as a kit together.

I tried:
1 RAM stick in each slot, all 4 worked fine.
2 RAM sticks in every combination (1 & 2, 1 & 3, 1 & 4, 2 & 3, 2 & 4, 3 & 4) none worked. The recommended one in the manual is 2 & 4.

I reset the CMOS and went back to BIOS defaults so XMP was disabled. Since this I have enabled it for now, but I'm only using 1 RAM stick.
Both sticks of RAM work fine as well when they're used individually but together they don't want to work.

The Mobo, RAM & CPU are all brand new. I had a few niggles installing the CPU and ended up bending a few pins on the CPU (male) but straightened them out and it runs fine.
To me it doesn't seem like the RAM is at fault nor the motherboard slots, as all 4 slots work individually.

Any ideas what else I can check? Maybe some BIOS settings that I may have missed?
 
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Aug 12, 2019
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Yes I straightened them all, no broken pins. I checked a few times over with a magnifying glass. Off the top of my head I think I only bent 3 or 4 pins in the corner, which I straightened with a needle & credit card.
 
Aug 12, 2019
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Do both memory modules work in each of the 4 slots (tested individually)?

Before I saw your note about bent pins, that is what I suspected. This is a classic symptom of such occurrences.
Yep that's right, both ram modules work in all 4 slots individually. If it matters, on the motherboard (female CPU socket) I couldn't see any visible damage in the holes using a magnifying glass. Am I right in saying that as long as there is a little bit of metal for the CPU pins to touch in the holes, it's OK?
 

COLGeek

Cybernaut
Moderator
Yep that's right, both ram modules work in all 4 slots individually. If it matters, on the motherboard (female CPU socket) I couldn't see any visible damage in the holes using a magnifying glass. Am I right in saying that as long as there is a little bit of metal for the CPU pins to touch in the holes, it's OK?
Theoretically, yes. But given the tight tolerances of the pins in relation to the socket, you may not be getting proper contact.
 
Aug 12, 2019
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Theoretically, yes. But given the tight tolerances of the pins in relation to the socket, you may not be getting proper contact.
If this is the case, could I put a tiny piece of metal in the motherboard holes that had bent pins to ensure that the male and female connectors are reaching each other? Similar to what Linus did in his video when he broke the pin (he just put the pin into the mobo side)
 
Aug 12, 2019
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Are there any other suggestions before I start sticking pins in my motherboard? I found an AM4 socket pin diagram but couldn't make sense of it
 

dorsai

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Nov 23, 2013
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Are there any other suggestions before I start sticking pins in my motherboard? I found an AM4 socket pin diagram but couldn't make sense of it
I'd recommend you not do that...it's nothing but a great way to short out the CPU or motherboard...unless you like expensive paper weights, because that's what you'll have.
 

dorsai

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Nov 23, 2013
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Sorry for the delayed reply, yes they're on the QVL. I have the CMK32GX4M2D3200C16 (2 of these). Still can't get both to work... Is this an RMA job for the motherboard?
It sounds like either the motherboard or the CPU...since you're able to see that the CPU pins are still attached after straightening I'd swap out the motherboard first. If you still have the problem after replacing the motherboard you're probably going to need to swap out the CPU as well.
 

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