RTX 5090 FE not detected on Z790 Maximus Extreme

[acowsik]

I purchased an RTX 5090 FE card last week and I have not been able to get it to work... the issue I am having is that the card powers up (fans spin and RTX logo lights turn on) but I don't get any display output and the VGA debug LED stays constantly on when the POST sequence checks for the GPU. This is with both DP and HDMI cables.

My system specs are as follows...

Intel i9 14900KS, ASUS Z790 Maximus Extreme (BIOS v3001 which is the latest on the product page), 64GB RAM, RTX 4090 FE (existing GPU), 1TB 980 Pro + 2TB 990 Pro SSDs, SB AE9 sound card, ROG PG32UQX display

The system works perfectly fine with my 4090 FE card but the 5090 isnt being detected at all in the BIOS (I have tried using the 4090 as primary and the 5090 as secondary and the BIOS only detects the 4090 GPU. For the secondary slot it doesnt show any speed like x8 /x16 like it does for my 4090 which is detected.

Have also tried changing the speed to Gen 3 and Gen 4 but didnt have any luck with that.

The 5090 however works perfectly fine at the test bed at the local service center (which is on an older system) and I even ran the UEFI firmware update tool there which updated but I still cant get the card to work.

I have done a CMOS reset as well as a BIOS reflash too and all power connections look fine and have tried reseating the card properly as firmly as it can go but no luck.

Any advice / suggestions would be greatly appreciated as I am not sure where the problem lies and am at my wit's end at troubleshooting this.

[Vynra]

did you try flashing to an older bios to see if that works?

[acowsik]

I wonder how would that help as a newer BIOS ideally should not break compatibility. I have gone through all the release notes of all the BIOS versions released in 2025 for my board and none of them ever mention anything about compatibility with 50 series GPUs. This is definitely a very weird scenario.

BTW the latest BIOS has a microcode fix for the CPU to improve stability so rolling back to an older BIOS somehow doesnt make sense to me especially when these microcode fixes are meant to avoid degrading of the CPU. This is something serious that ASUS need to look at ASAP and provide a BIOS fix so that these new cards can work.

This kind of incompatibility with barely 2 yr old hardware despite all due diligence from my part is just plain unacceptable.

[Silent_Scone]

Hi @acowsik 

Can you confirm whether the 5090 is installed directly into the motherboard PCIe slot (no riser or vertical mount)? Also, how are you powering it in your system, are you using the dedicated 12VHPWR cable(s) straight from the PSU, or supplied adapters? Since it worked fine at the service centre, just want to check if there’s any difference in how it’s hooked up between your rig and theirs

[acowsik]

5090 is directly installed into the board PCIe slots the usual horizontal way. Power to the card is using the power cable that came with the card as that is how it was tested at the service center as well just to be on the same page.

The service center only had like a 750W PSU while I am using a 1500W Corsair HX1500i unit with 4 separate PCIe 8 pin cables for each of the 4 connectors that the provided adapter cable needs.

My 4090 however uses the Corsair cable that uses 2 8 pin connectors on the PSU side and the 12VHPWR connector on the GPU side. I tried using that one as well as the cable that was used at the service center as well but no luck with either.

I have my doubts that it is a PSU related issue else I would have had weird instability even with my 4090 which I have been using for over 2 yrs.

[acowsik · Accepted solution]

Finally got it all working... removed the board from the case, refitted it back and then reinstalled everything again... this seemed to do the trick...

Guess there might have been some sort of misalignment or what not but am glad its all over with. Whew....