Asus Crossfire X870E - m.2 usage and PCIE16_1

[ESzczesniak]

I am setting up a new build. I have 4 x m.2 SSD’s. I also have a RTX 5090 and a PCIE2x4 expansion card…in other words need both PCI slots. 

If I’m reading this correctly, to use all m.2 drives and keep both PCIE slots enabled, I can only use m.2 1, 3, 4, and 5?  

And if I want PCIE16_1 to remain gen 5 x 16, I can only use m.2 1, 4, and 5?  

I want to verify I’m understanding this correctly before looking for a solution for my 4th m.2 drive. 

This is all going to be used for flight simming and sim racing. So maybe I won’t notice x8 vs x16 on PCIE5? But seems stupid to handicap the big honking graphics card. 

[Mr_Savy]

I had the same situation and this was my solution.  I included CystalDiskMark speeds.

Slot #1: Samsung 9100 Pro (14,607/9323 R/W)

Slot #4: WD SN850X (6894/4827 R/W)

Slot #5: WD SN850 (6922/2551 R/W)

Samsung 980 Pro (6825/4034 R/W):  AMPCOM M.2 NVME SSD to PCIe 4.0x4 Adapter Card w Copper Cooling for Desktop PC (PCI-E Gen 4 Full Speed 64Gbps) bought from Amazon $13.49

Everything runs at full speed or close.  I also use my system for MSFS, sim racing, + online multiplayer games, local first person shooters.  My system is x870e-e, 9800x3d, Asus 5080 TUF oc

[ESzczesniak]

Thank you for the reply! Unfortunately, that leaves me unable to use the second PCI-E slot for a USB expansion. 

My flightsim setup includes an almost full F/A-18C out running bunches of arduinos. So I actually can max out a USB controller. 

I’m also not sure if the x8 vs x16 matters much in gaming on Gen 5. Back when the 4090 came out, I know it was known that it didn’t fully saturate the gen 4 x 16 and dropping to x8 or gen 3 only was a 1-2% drop in performance. I haven’t found similar stats for the 5090. But x8 on gen 5 is the same as gen 4 x 16. 

[Mr_Savy]

Very cool setup you have and wish I could see it.  More sophisticated than my setup which uses a Saitek x52, iphone (head movement), & ipad  (flight instrumentation).  Also have a Logitech G923 for sim racing.  Let us all know how you solve your issue.

[Mr_Savy]

One other inspiration.  How about using an external USB4 hub.  I don't use one but I've seen hubs with various configurations that might meet your needs.  Just a thought.

[ESzczesniak]

That I have to look in to more. The issue is USB controllers. Each controller can theoretically control 127 devices. But some devices are 3-4 USB VID’s (128 buttons, under 4x32 USB devices), hubs take at least one, etc.  It seems obnoxious to take that many USB, but some things like the back up ADI are their own separate Arduino. So it adds up. 

So I need to see if that’s just simply a hub, or another USB controller. 

[Mr_Savy]

What about this thought for your USB PCIe card.  From what I have read this should work. A user said "Should work, I've put all kinds of stuff in my eGPU enclosure: network cards, USB controllers, NVME SSD's, Areca RAID controllers, Intel QAT card, etc."  I guess you'll have to determine which is your most appropriate route;  m.2 drive taking lanes from the GPU or a full speed GPU but with only one usable PCIe slot (for m.2) + an external PCIe enclosure (USB PCIe).

eGPU Enclosure Thunderbolt 3/4 USB4 40Gbps PD 85W Charging External GPU Dock Compatible with NVIDIA/AMD Graphics Cards on Win 10/11 Linux System, ATX Power Supply (MK-L18) or something like this

[ESzczesniak]

That’s definitely a thought. m.2 won’t saturate a USB4 port, so theoretically should be fine to put those external. And use 1, 4, and 5 which should keep the top PCIE at x16. 

I did read one discussion that suggested using the bottom PCIE slot will put both in to x8. I’m not clearly seeing that in the manual, but if that’s true it’s a moot point unless I’m willing to give up the PCIE USB card.