Figured out Asus Motherboard loss of tracking (grey screen) issues.

[GlaucomaPredator]

I have had loss of tracking issues since 2016 on this motherboard (Asus Rampage V Extreme), first with the HTC VIVE, which I sold a while ago, and now with the Valve Index.
I have this mobo paired with an intel i7 5930k which has 40 PCIe lanes.

PCIe lanes and shared bandwidth is something you may want to consider when troubleshooting your loss of tracking issues. For me it came down to bandwidth limitation, even though I was using USB3.0 and a 40 PCIe lane CPU there is a limitation on this high end motherboard. So if your mobo is mid range and your CPU has even less PCIe lanes, primarily Intel CPUs, you may have more restrictions and limitations on your hardware.

Essentially what was happening is that a PCIe slots shared bandwidth with my USB3 9-10 ports. Port 9/10 is where I had my HMD connected, and this slot shares bandwidth with the PCIe slot where my PCIe nvme raid card was connected, this is also where I have HL Alyx and most of my games installed. So when the game was loading assets and resources I would see loss of tracking, or the dreaded grey screen.

Turns out that the certian PCIe lanes and USB ports get disabled on the motherboard, or share bandwidth depending what PCIe device is plugged in and what pci speed it operates at.

So something you have to consider when troubleshooting your grey screen is, how mana PCIe lanes does the CPU have, how many does the motherboard support, where if any bandwidth is being shared with PCIe lanes. What devices you have plugged in the PCIe bus and on which ISB port does your HMD sit.

Here is an excerpt from my mobo manual....

"The PCIE_X4_1 slot shares bandwidth with the PCIE_X1_1 slot, USB3_E910, and SATAexpress_E1 connector."

It not only shares bandwidth but it also disables the USB3 ports if a X4 speed device is plugged into that slot.

Some people thing that plugging in an external USB3.1 card is the solution, it can be but only if your USB3 card is not interfering with other devices and the bandwidth is not being shared with other on board devices. Your CPU also needs to have enough PCIE lanes to support populating the specific slots because this is from my mobo manual on the same page....

"The PCIE_X8_4 slot shares bandwidth with M.2 x 4. When PCIE_X8_4 is occupied, the M.2 will be disabled."

also

"The PCIE_X8_4 slot will be disabled when using a 28-lane-CPU"

Pick and choose where you plug in your HMD wisely.

TL:DR Your CPU and Mobo have PCI lane limitations, depending on what device you have plugged into what PCIe slot it may be limiting USB3 speeds and disabling other devices. Basically RTFM.

[--ranXerox--]

yup! Very important key points. What sometimes fixes these issues like what I seen is if the manufacturer still supports the device, update the firmware, and also the driver packages. I seen these fixed by these measures but you are basically screwed if the lanes are shared and they stopped support.

Also, I want to add that if your motherboard comes with bad shielding like usb or pci-e, the bandwith will leak and cause other parts of your device to stop normally functioning.

Good example is the asus ac-68u wifi where they sent out a firmware to disable the usb 3.0 and forced usb 2.0. This is because the ethernet was right above the usb ports and leaked signal. Long story regarding this but this is also true of motherboards.

asrock X570 Steel Legend WiFi ax is a good mobo and i have not found any issues. I recommend it if anybody is shopping around especially with an amd 3700x. use 16gb ram, and don't bother with 32gb ram. Your pc will crash, FYI.