Question Next Steps to Solve B1 and B2 Slots Not Working?

Sep 1, 2020
5
0
10
0
I built a new PC last week and while everything runs smoothly, I can only use one stick of RAM because the B1 and B2 slots don't read the second stick.

Troubleshooting Steps Taken So Far:

- Unbent a few bent CPU pins

- Replaced RAM sticks and confirmed both boot up the PC in slots A1/A2

- Tried RAM sticks in B1/B2 slots -- No bootup

Build:
CPU: Ryzen 9 3900X
Motherboard: UD X570
Memory: Corsair Vengeance LPX

Is my next step just to buy a new motherboard? Thanks for the help
 

Darkbreeze

Retired Mod
You are using the wrong slots. A2 and B2, the second and fourth slots over from the CPU socket, are the slots that BY DESIGN must be used for any TWO DIMM configuration on modern dual channel motherboards. ALL modern dual channel motherboards.

Move your DIMMs to the second and fourth slots.

If the memory doesn't work when those slots are populated then your problem stems from your bent pins.
 
Sep 1, 2020
5
0
10
0
You are using the wrong slots. A2 and B2, the second and fourth slots over from the CPU socket, are the slots that BY DESIGN must be used for any TWO DIMM configuration on modern dual channel motherboards. ALL modern dual channel motherboards.

Move your DIMMs to the second and fourth slots.

If the memory doesn't work when those slots are populated then your problem stems from your bent pins.
I should've mentioned that I normally boot up with RAM in the 2nd and 4th slot. Problem is the memory only posts in the A2 slot. I can look again to see if there are bent pins, but I thought I had fixed those already
 

Darkbreeze

Retired Mod
"Fixed" is a pretty subjective term. On AMD processors where the pins are ON the CPU, rather than on the motherboard like they are for Intel, it is not uncommon for a pin to break IN the CPU, where you can't see it, when straightening pins. Or, if the system was previously run WITH the bent pins, then there could be any number of other issues present, not least of which is damage to the motherboard.

But it would be a good idea, at least initially, to see that you don't still have any bent pins before going any further. Then, also while you're at it, gently check any of the pins that were bent to see if they easily "wiggle" at all. If they do, then the CPU is shot.
 
Last edited:
Sep 1, 2020
5
0
10
0
"Fixed" is a pretty subjective term. On AMD processors where the pins are ON the CPU, rather than on the motherboard like they are for Intel, it is not uncommon for a pin to break IN the CPU, where you can't see it, when straightening pins. Or, if the system was previously run WITH the bent pins, then there could be any number of other issues present, not least of which is damage to the motherboard.

But it would be a good idea, at least initially, to see that you don't still have any bent pins before going any further. Then, also while you're at it, gently check any of the pins that were bent to see if they easily "wiggle" at all. If they do, then the CPU is shot.
Yeah I figured the CPU could still be an issue. I’ll definitely check it out. Thanks for the help
 
Last edited by a moderator:

Darkbreeze

Retired Mod
The bottom line is, for a lot of modern boards, if you try to run a pair of DIMMs in the A1 and B1 DIMM slots without anything installed in A2 and B2 slots, you may get a variety of different results ranging from works fine to won't work at all, to anything in between. It seems to be pretty uncommon these days for those slots to work properly though if the primary slots are not populated.
 
Sep 1, 2020
5
0
10
0
The bottom line is, for a lot of modern boards, if you try to run a pair of DIMMs in the A1 and B1 DIMM slots without anything installed in A2 and B2 slots, you may get a variety of different results ranging from works fine to won't work at all, to anything in between. It seems to be pretty uncommon these days for those slots to work properly though if the primary slots are not populated.
Yeah they B slot doesn’t post regardless if I position in A1/B1 of A2/B2. I should note that there’s an error message when booting up with two sticks: “PMU memory training error at socket zero channel 1 DIMM 1.” That same error doesn’t appear when I use only a single stick of RAM in the A2 or A1 slot
 

Darkbreeze

Retired Mod
That sounds like a CPU problem. It could be damage, but it sounds like a problem with the CPU. One option might be to obtain a very cheap, but compatible CPU and try it to see if you still have the same problem or not. If not, then you know the CPU is the problem. If you do, then you know it's not the CPU and can then either swap out the motherboard or the memory. I assume you have tried BOTH DIMMs, individually, in that B2 slot, and both dimms individually in the A2 slot, and that both worked in the A2 slot but both failed in the B2 slot?
 
Sep 1, 2020
5
0
10
0
That sounds like a CPU problem. It could be damage, but it sounds like a problem with the CPU. One option might be to obtain a very cheap, but compatible CPU and try it to see if you still have the same problem or not. If not, then you know the CPU is the problem. If you do, then you know it's not the CPU and can then either swap out the motherboard or the memory. I assume you have tried BOTH DIMMs, individually, in that B2 slot, and both dimms individually in the A2 slot, and that both worked in the A2 slot but both failed in the B2 slot?
Yeah I tried that. Also got new memory so I don’t think that’s the problem. Will definitely check out the CPU
 

ASK THE COMMUNITY

TRENDING THREADS