[solved] PC hangs on "Enter BIOS" screen when Valve Index DisplayPort is plugged in

[cyvern]

Hi,

I recently received a Valve Index (it's amazing), but I'm having one issue: I can't boot my PC when the DisplayPort is plugged in, it stays on the "Press F2 or DEL to enter UEFI BIOS" screen forever. It doesn't load an OS, and pressing the keys to enter BIOS does nothing. It just hangs there indefinitely.

When the DisplayPort is unplugged, the PC happily boots fine again. The USB remains connected, it doesn't seem to be causing the issue.

I have a Windows/Linux dual-boot system. Normally the first thing I see is the Linux bootloader menu to select what OS I want. I have tried changing my boot preferences in bios so that it boots directly into the Windows. This makes no difference.

This happens regardless of which DisplayPort my Index is plugged into. My GPU has three DPs and one HDMI which my monitor is plugged into.

Fast Boot is disabled in BIOS.

Right now I'm just plugging and unplugging it as needed. I would really appreciate if anyone has any ideas on how to fix this.

Thank you ^^

my specs:
cpu - Intel Core i5-7500
gpu - Radeon RX 5700 XT
mobo - Asus Prime B250M-A

[rawWwRrr]

I'm only guessing as I don't have a Valve Index... possibly set the primary display in the BIOS from Auto to your monitor port?

[[☥] - CJ -]

Faulty DP cable maybe?

[_I_]

or weak psu

[cyvern]

so my bios doesn't seem to support setting the primary display, however I searched this and it lead me to something that seems to have fixed it. It looks like disabling/enabling CSM (a legacy support thing I think) changes the preference order for different types of graphics ports.
So I enabled CSM and now my PC boots with my Index DisplayPort plugged in! :3 Not sure why, I think maybe it was treating my DisplayPort Index as the primary display which freaked it out and is now treating my HDMI monitor as the primary display like it should be? Either way, it works now, which is awesome. Thanks a lot for your help ^^
Appreciate the other suggestions, I'm glad it doesn't seem to a faulty/underpowered hardware problem in my case but they definitely would have been something to investigate if I had exhausted all the bios config options and still was having problems.