Motherboard PCIEx16 top slot is only x1 while bottom slot is x4. Its bottlenecking my 3080

[Panda654]

The initial thread started here but then I figured out the bottleneck. It was PCIE rather than my CPU/RAM or anything.

For some reason, my top slot only gives x1 lane while the bottom one gives x4. Moving from top to bottom slot doubled my FPS but still not what the 3080 or my CPU is capable of.

 

My NVME SSD is connected in the top m.2 slot while I only have 1 SATA connection in port 1.

 

I would appreciate any help

 

System:

GPU: MSI Trio Z RTX 3080 10GB

CPU: Intel i7-9700k

Mobo: MSI Mortar B360M

Ram: 4x8GB Kingston HyperX (run at 2400mhz)

Storage: Samsung NVME 980 1TB (boot) ; 2TB seagate HDD (steam lib)

PSU: Corsair RM750x

Monitor: Viewsonic 1440p 32" 60hz 

OS: Windows 10  22H2

[CommanderAlex]

Why not move the NVMe SSD down to the second M.2 slot and install the 3080 in the first PCIeX16 slot?

[Sarra]

Your top 16X slot is wired for 16 lanes. The bottom is wired for 4 lanes.

 

You should use the top slot.

 

The top slot has dedicated lanes. If they aren't available, you need to figure out why; I'd suggest cleaning out the PCIE slot, make sure the PCIE power plugs (8 pin) are all plugged in, and if you still only show 1 lane to that top slot, then you need to reseat your CPU. Pull the cooler off, pull the CPU out of the socket, and make sure there are no bent pins in the CPU socket.

 

If it still only has 1 lane, you should contact MSI about RMAing the board.

[CommanderAlex]

13 minutes ago, Sarra said:

Your top 16X slot is wired for 16 lanes. The bottom is wired for 4 lanes.

 

You should use the top slot.

 

The top slot has dedicated lanes. If they aren't available, you need to figure out why; I'd suggest cleaning out the PCIE slot, make sure the PCIE power plugs (8 pin) are all plugged in, and if you still only show 1 lane to that top slot, then you need to reseat your CPU. Pull the cooler off, pull the CPU out of the socket, and make sure there are no bent pins in the CPU socket.

 

If it still only has 1 lane, you should contact MSI about RMAing the board.

M.2 is going to take 4 lanes so it leaves 12 left as the 9700K has 20 total, but 4 lanes go to the chipset. Overall, OP should install graphics card in the top PCIe slot and leave the M.2 in the lower M.2 slot and have it run through the chipset. Yes, you may see an impact on performance but it's a tradeoff you have to take. 

 

I doubt the motherboard is still within warranty if the OP purchased it when 9th gen Intel was the latest.

[Sarra]

Just now, CommanderAlex said:

M.2 is going to take 4 lanes so it leaves 12 left as the 9700K has 20 total, but 4 lanes go to the chipset. Overall, OP should install graphics card in the top PCIe slot and leave the M.2 in the lower M.2 slot and have it run through the chipset. Yes, you may see an impact on performance but it's a tradeoff you have to take. 

 

I doubt the motherboard is still within warranty if the OP purchased it when 9th gen Intel was the latest.

The lanes from the top PCIE slot go directly to the CPU.

 

The M.2 does not share lanes with the PCIE slot, they are also dedicated.

 

If the top 16X slot is running at anything other than 16X, then there is something wrong. Having an M.2 in the top slot should not effect the number of lanes the top 16X slot has available.

 

I gleaned this information from MSI's official specs page for this board. If the top 16X slot shares lanes with the M.2, it's not shown in their specs.

[CommanderAlex]

25 minutes ago, Sarra said:

The lanes from the top PCIE slot go directly to the CPU.

 

The M.2 does not share lanes with the PCIE slot, they are also dedicated.

 

If the top 16X slot is running at anything other than 16X, then there is something wrong. Having an M.2 in the top slot should not effect the number of lanes the top 16X slot has available.

 

I gleaned this information from MSI's official specs page for this board. If the top 16X slot shares lanes with the M.2, it's not shown in their specs.

Yes, that's correct.

 

The lower M.2 slot uses the chipset, which has it's own set of PCIe lanes dedicated from the CPU (Between CPU and chipset-4 lanes). Apparently, both are run through the chipset using a "switch" of some sort. 

 

This is the block diagram directly from the manual. 

 

[Mister Woof]

Clear your BIOS; could have somehow set to only 1x