PC won't boot properly with displayport cable plugged in

[shyeet]

So I have an RTX 3090 on an old motherboard (MSI Z97 Gaming 9 AC). The motherboard has a lot of issues when booting (freezes on POST code 99 and 92). When I try to boot with a UGreen DP 1.4 cable plugged into the GPU, I either get no output to my screen, or the POST freezes on initialization code 92.

When I plug in an HDMI cable and boot with that, I get output to my display, and the PC is more likely to boot. (still sometimes freezes on POST code 99 and 92).

Is this a motherboard/BIOS issue? I've tried turning on MSI fast boot and the Windows 10 compatibility mode in BIOS, which resulted in little improvement.

I've ordered an AM5 upgrade kit (because the current MOBO, RAM and CPU are quite old anyway), hoping to fix the issue. But I am afraid of this being a GPU issue or something.

 

[shyeet]

I bought the PC on carb, thread is here:

[For Sale] - RTX 3090 Gaming PC + NAS | Combo (multi-item) sales & full systems

Item: RTX 3090 Gaming PC + NAS CPU: Intel Core i7-4790K with Corsair H100i liquid cooler. Motherboard: MSI Z97 Gaming 9 AC RAM: 32GB DDR3 2133 MHz (2x 8GB G.Skill F3-2133C10-8GSR + 2x 8GB Corsair CMY16GX3M2A2133C11) GPU: Palit GeForce RTX 3090 GamingPro OC Case: Corsair Special Edition White...

carbonite.co.za

Is this simply a case of old hardware i.t.o. the motherboard, ram and CPU?