Connecting M.2 directly to motherboard or via PCIe expansion card

longe

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Nov 22, 2017
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I have an Asus PRIME Z270-A motherboard and I'm using all 6 SATA ports (1 SSD, 4 mechanical drives, 1 optical drive). I also have a Gigabyte Nvidia GTX 1050Ti 4GB graphics card.

I'm looking at buying the Samsung 960 Evo M.2 SSD.

Initially I planned to connect it via 1 of the 2 M.2 slots built into the motherboard. However, 1 of the M.2 ports will disable 2 of the SATA ports (no good) if running at x4 speed and the other M.2 port I believe will be ok because it is a PCIe M.2 drive. If it was a SATA M.2 drive it would disable 1 of the SATA ports.

So if the above do end up disabling SATA ports, the alternative is to buy a M.2 adaptor card that plugs into a PCIe connector on the motherboard. Question here is what lanes does this use? I'm aware that the graphics card currently uses 16 of the 16 GPU lanes, but will an M.2 adaptor card use GPU lanes (because it's connected via a PCIe port) or some of the 'other' lanes?
 
Solution
The M.2 adapter card will use the PCIe lanes that are available to the PCIe slot it's plugged into. The 2nd x16 slot has 8 PCIe lanes [x8], the 3rd x16 slot has 4 PCIe lanes [x4] and the single PCIe slots have 1 lane [x1].

Also keep in mind the number of lanes the adapter card uses also depends on the card itself. All the cards i have seen are either PCI Express x2 or PCI Express x4. If the card itself is x4, it can't use all the 2nd PCIe slots 8 lanes.
The M.2 adapter card will use the PCIe lanes that are available to the PCIe slot it's plugged into. The 2nd x16 slot has 8 PCIe lanes [x8], the 3rd x16 slot has 4 PCIe lanes [x4] and the single PCIe slots have 1 lane [x1].

Also keep in mind the number of lanes the adapter card uses also depends on the card itself. All the cards i have seen are either PCI Express x2 or PCI Express x4. If the card itself is x4, it can't use all the 2nd PCIe slots 8 lanes.
 
Solution