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Question Getting ready to add a 3rd (?) PCIe M.2 drive to an Asus Prime Z370-A


I already have two 970 Evo M.2 drives installed in M.2+1 and M.2_2 (second drive configured in BIOS as PCIe rather than SATA).

I just picked up a third M.2 drive to replace the one in the M.2_2 slot with double the capacity, but thought maybe I would just add it using the PCIe NVMe expansion card (has an x4 connector) I had to buy anyhow because I needed it to copy the drive on M.2_2 over to the new M.2 drive. Then I thought to myself "Self, maybe it would be ok to run with all the drives?"

What this means is I'll be sharing the PCIe bus with three NVMe M.2 drives and a 2080 Ti on an Asus Prime Z370-A motherboard.

Has anyone done this? Run three PCIe M.2 drives on Z370 in conjunction with their graphics card?

Does it turn your primary graphics card slot into an x8 even though it goes into an x4 PCIe slot? Are there huge GPU performance hits for doing so?

Should I stay with my original plan of replacing the old drive of half the capacity? What's your opinion?

I'm going to try it, but I wanted to find out anyone else's experience with this situation to gather data for the science of it all.

Thanks in advance!
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There should be very little if any performance hit running the GPU in x8 mode.

You could install the card in the PCIeX16_3 slot. Let it share the bandwidth of other chipset devices. How often are you going to have enough devices under load to overwhelm the x4 lanes shared by the chipset?

If using a card in the PCIeX16_2 slot. I'd want one which handles multiple SSD. So as all NVMe SSD get dedicated CPU PCIe lanes. 2 via PCIe card and one via M.2_1. Assuming this is possible. As it says for 3x PCIe SSD you have to use a Hyper M.2 card in PCIeX16_1 and disable PCIeX16_2. But that may just be for some special configuration.

The best you may be able to do is two M.2 to CPU SSD and one M.2 to Z370 SSD. Although I'd opt for one to CPU and two to Z370. Unless you are doing frequent intense work to your secondary SSD.
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The expansion card I have is pretty basic. It powers a single PCIe M.2 drive and a single SATA M.2 drive with a SATA connection on the card to connect to the SATA bus. I don't think I'd ever use an M.2 drive over SATA, but if I ever need the extra connection (e.g. for copy operations) I have it.