[SOLVED] Installing multple m.2 drives

nes

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May 3, 2012
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Hello, I want to have 3 or more m.2 drives installed into my pc, but I only have 2 m.2 ports on my motherboard(ASUS rog crosshair 8, with a 5900x). I will use this pc for gaming and would like mass storage for games and multimedia recording my gameplay. I would like to purchase a 'ASUS hyper m.2 gen 4 m.2x16 gen 4 card' for the extra m.2 ports. Would this pcie adapter steal all the bandwidth on the motherboard since I also have the 2 m.2 already in use? I am afraid that I will artificially bottleneck my gpu (rtx 3070 I will upgrade when the 3090 is easily purchasable) by using this pcie adapter. I am switching from the x570 aorus master 3 m.2 to x570 rog crosshair 8 2 m.2. The aorus motherboard was giving me problems and there were other issues that bothered me.
 
Solution
It should be fine to populate all 3 M.2 slots on your motherboard while having a 3070/3090, the bottom two M.2's should be able to route through the chipset alleviating any bottlenecks (typically using all 3 m.2 slots will disable your lowest PCIe slot). When you install the M.2 riser card however, you may need to bifurcate the top two PCIe slots from a 16-8 to an 8-8 mode. You can do this in the BIOS easily, this way you can prevent bottlenecking your system if it seems like it's chugging. You may have a slight performance drop on gaming but nothing substantially noticeable (varies on the game). Since your board is Pcie 4.0 capable it should be able to handle all the throughput, since every lane is essentially double the speed of 3.0...
It should be fine to populate all 3 M.2 slots on your motherboard while having a 3070/3090, the bottom two M.2's should be able to route through the chipset alleviating any bottlenecks (typically using all 3 m.2 slots will disable your lowest PCIe slot). When you install the M.2 riser card however, you may need to bifurcate the top two PCIe slots from a 16-8 to an 8-8 mode. You can do this in the BIOS easily, this way you can prevent bottlenecking your system if it seems like it's chugging. You may have a slight performance drop on gaming but nothing substantially noticeable (varies on the game). Since your board is Pcie 4.0 capable it should be able to handle all the throughput, since every lane is essentially double the speed of 3.0, which is already adequate for a 3090 as is.
 
Solution
It won't steal bandwidth from the motherboard m.2 slots, but will use some of the PCIe channels now going to your video card. Assuming you plug the expansion card into a PCIe x16 slot it will split the PCIe channels from your video card so both the video card and the expansion card will get PCIe x8 bandwidth. Given your video card doesn't need more than PCIex8 anyway under normal conditions you shouldn't see a performance hit.