Question Can't access Multi-monitor (iGPU) setting in BIOS when set to CSM (Legacy Boot)

[ravv]

I can only boot into Windows 11 if I have CSM (Legacy Boot) on, otherwise I get a hanging black screen. Also if I have CSM on - I can boot into BIOS, however iGPU is inaccessible!


I would rather have a UEFI boot, but as stated, if I set it to that ¹I can't boot into Windows, and ²I can't access the BIOS!...so might have to settle for some way to keep CSM enabled whilst finding some way to get the iGPU (multi-monitor) setting to appear in the BIOS.

I am using an Asus Z790 motherboard, and it's brand new after I changed a previous model which had the same issue.

Help required!


nb. The only way I could get back into the BIOS originally if I had the PC set to UEFI boot/black screen, was to completely turn off the PC, then press the Clear CMOS button on the motherboard, then turn the PC back on, and access the BIOS as normal with repeated presses of the DEL key - with which I then set the PC to CSM boot (where I am with it now).

 

[Lutfij]

I am using an Asus Z790 motherboard, and it's brand new after I changed a previous model which had the same issue.
Asus is the brand of the board, while Z790 is the chipset for said motherboard. What is teh model of the board? What BIOS version are you on?

On second thoughts, please pass on your full system's specs like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time. Sig space specs can and will change over time, when that happens this thread and it's relevant suggestions will be rendered moot to the end user in the same boat as you're in now.

You mentioned swapping the boards, what board were you on prior?

 

[ravv]

Thanks for reply. Here's your questions answered:

• CPU: Intel Core i7-14700K
• CPU cooler: Deepcool LT720 360mm
• Motherboard: Asus ROG STRIX Z790-A GAMING WIFI II
• Ram: Kingston Fury Beast RGB DDR5
• SSD/HDD: Main Windows Boot SSD = WD SN850X 2TB
• GPU: MSI GeForce RTX™ 4070 VENTUS 2X 12G OC
• PSU: Antec NE850G M ATX3.0
• Chassis: NZXT H7 Flow RGB
• OS: Windows 11 Pro
• Monitor 2 (Identified in Windows display settings) - (Gaming Screen, connected to the one GPU HDMI port): Asus TUF VG259QM (Connected Pass Thru from AVerMedia AVT GC575 Capture Card for OBS (plugged into the GPU))
• Monitor 1 (Identified in Windows display settings) - (Primary Monitor, connected to one of the three GPU DisplayPorts): Asus ROG XG259QNS

The PSU is less than 6 months old (PC built in March 2024).
BIOS v.1503 (re. CPUID ROG CPU-Z).
Previous motherboard = Asus Z790-H.

Hope this helps?

ps. Incidently, I saw others with this issue through a browser search (Reddit):

https://www.reddit.com/r/iBUYPOWER/comments/my2yvy/no_igpu_option_in_asus_uefi_bios_please_help/

EDIT: Just had a thought, and the PSU has a Hybrid Mode button. Apparently pressed in means Fan Always On - which is how I have it set. Probably nothing to do with this anyway..
Also, I am upgrading the CPU cooler to a Deepcool Mystique 360mm this week.

 

[Lutfij]

I know that if your iGPU is enabled in BIOS while you're hooked to your discrete GPU ports you might end up with a black screen as I've learned with my AM5 platform, the only way to see the BIOS screen is to have a display hooked to the iGPU's ports, before the system POST's.

My question now is, how did you install the OS? If you installed it with CSM enabled or you changed to CSM and are now unable to boot to the OS, then you will need to reinstall the OS, per my understanding. CSM should also be disabled by default(after you fire up the board for the first time), per my understanding.

 

[ravv]

My understanding of you saying 'iGPU ports' is either the HDMI or DisplayPort of the motherboard, and not the NVidia dGPU. Is that correct?
I have the main screen (screen 1 in Windows) hooked up to the DisplayPort of the dGPU.
I don't want to have to keep unplugging and plugging cables in order to be able to see the BIOS screen. Besides, I just don't want to use the motherboard graphics ports when I have a dGPU.

To answer your question - I installed the OS as normal ie. where CSM would be disabled by default. Like you said, CSM is disabled by default by the motherboard, so I have no idea why the PC is wanting to boot like this.

I just thought tho that because I have changed motherboards recently and removed the boot SSD from the the original install motherboard and plugged it into the new one - would that affect things?

Obviously, reinstalling the OS would be the last thing I want to do, as that would mean a heck of a lot of third party installations afterwards that I'd rather avoid getting into as it would take me a long time to replicate my customization as it is now.

 

[ravv]

My understanding of you saying 'iGPU ports' is either the HDMI or DisplayPort of the motherboard, and not the NVidia dGPU. Is that correct?
I have the main screen (screen 1 in Windows) hooked up to the DisplayPort of the dGPU.
I don't want to have to keep unplugging and plugging cables in order to be able to see the BIOS screen. Besides, I just don't want to use the motherboard graphics ports when I have a dGPU.

To answer your question - I installed the OS as normal ie. where CSM would be disabled by default. Like you said, CSM is disabled by default by the motherboard, so I have no idea why the PC is wanting to boot like this.

I just thought tho that because I have changed motherboards recently and removed the boot SSD from the the original install motherboard and plugged it into the new one - would that affect things?

Obviously, reinstalling the OS would be the last thing I want to do, as that would mean a heck of a lot of third party installations afterwards that I'd rather avoid getting into as it would take me a long time to replicate my customization as it is now. I do use Acronis - which has also started playing up since I've changed boards - in order to backup and restore my whole system; but that would also backup and restore this CSM thing, so doubt that would help with a total reinstall of the OS and quick restore of my programs.

I just would rather not go down that route and thought there might be some other way to fix this?

In fact, a problem I have is that I can't even boot into Windows if I enable UEFI in the BIOS - so I wouldn't know how I'd be able to reinstall Windows with a non-CSM BIOS anyway.