Which slot to use for a M.2 PCI-E adapter?

[Frenky]

So I'm looking to add extra storage and I have already used up both m.2 connecters on the board, so I'm planning on using a M.2 PCI-E adapter to add another drive but I'm unsure where to slot it in. 

 

This is a picture of my X370 Taichi board. The red circles mean the slots are occupied, the blue ones are free. Where do I put the PCI-E adapter? Does this matter at all?

 

[Levent]

If you add more PCIE devices, either:

• the device you add is not going to be detected.
• or your graphics card is going to run at PCIE x4 (most likely this).

If you still going to do it, put in the last slot or the third pcie slot (first blue PCIE x16 one), but just so you know, you gonna be leaving some performance on the table in games if you add another NVME.

[RONOTHAN##]

The bottom slot is disabled when the bottom M.2 slot is occupied.

 

The next slot up is a PCIe Gen 2 slot with only 1 lane of bandwidth, so you'd be running at 1/8th the max bandwidth of whatever SSD you get.

 

Next slot up will take 8 lanes away from your GPU, but if you have any GPU lower than a 1080 Ti it doesn't really matter. This is probably your best option.

[manikyath]

this is where the motherboard manual is actually helpful:

https://download.asrock.com/Manual/X370 Taichi.pdf

 

page 25 has some details about which slot conflixts with what:

Quote

PCIe slots:

PCIE1 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.

PCIE2 (PCIe 3.0 x16 slot) is used for PCI Express x16 lane width graphics cards.

PCIE3 (PCIe 3.0 x16 slot) is used for PCI Express x8 lane width graphics cards.

PCIE4 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.

PCIE5 (PCIe 2.0 x16 slot) is used for PCI Express x4 lane width graphics cards.

* If PCIE5 slot is occupied, M2_2 will be disabled

slot 5 (the very bottom one) is shared with the bottom M.2 slot, so that one is out already.

it also mentions that slot 2 and 3 (the GPU one and the other big one) are sharing 16 CPU lanes, so if you use slot 3 you're cutting GPU lanes in half.

 

so i suppose this means either of the 1x slots. i dont directly find a note that either one of these are shared with anything else, so i suppose both are fair game.

[Frenky]

Oh crap! Good thing I asked. Thanks so much for the help guys!