Why can't I disable CSM??

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benetard

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Jan 25, 2014
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Just put together a new system and it is booting up fine. The problem is if I disable CSM it won’t POST. I’ve narrowed it down to the Video Oprom setting. It will only boot if it is in legacy mode.

This is all brand new hardware so surely it should be able to go 100% UEFI. I’ve seen others with this mobo who are disabling CSM just fine. I have a GTX 1080Ti and I don’t understand why it needs legacy mode. Right now it is outputting HDMI to a Hisense 4K TV. I don't have another display to try right now.

Specs:
ASRock x399 Professional Gaming
Threadripper 1950x
32GB G.Skill DDR4 PC3200
EVGA GTX 1080Ti SC2
3x Samsung 960 Pro 1TB M.2

(Please note this has absolutely nothing to do with Windows. I am not even to the point of installing an OS yet.)
 
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benetard

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Jan 25, 2014
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Disabling CSM is required for bootable NVME RAID.
 
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jr9

jr9

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Dec 6, 2017
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Well disabling it can cause even newer hardware to not work and the motherboard manual asks that it should never be disabled except during a WHCK test (or never basically). Have you tried setting up the RAID with CSM enabled?
 
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benetard

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Yes I was able to install Windows 10 on RAID. But for example I can't use Fast boot or secure boot unless CSM is disabled.

It sucks that I can't use all the features of the mobo that I paid for. But from what I've been reading it seems like this whole platform is incredibly buggy.
 
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jr9

jr9

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One thing you could try in your UEFI setup utility:

Boot tab - > CSM - > Set to enabled

then set "Launch PXE OpROM Policy" to UEFI only.

Try experimenting with those policy options. They give you control over how CSM works. Perhaps with PXE or something else set to UEFI only it will enable you to select fast boot.

It's very odd a system with new parts as this one won't POST without CSM. GTX 1000 series are all definitely GOP compatible. If you haven't already try flashing your BIOS.
 
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benetard

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Jan 25, 2014
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I have both PXE and Storage set to UEFI. The fast boot option is available and when I choose it it makes the CSM option disappear altogether. (I assume this means it automatically disables CSM) And sure enough I get the same black screen when I enable Fast boot.

I just tried a EVGA GTX 1080 FTW from another system and it was able to boot with CSM disabled, but then it needed two boots to get into Windows after that. And I tried to get back into the BIOS with the "reset to UEFI" windows tool from Asrock but it didn't work. So the only way I could get back into BIOS was clearing CMOS.

I have the latest 2.0 bios for the mobo and I don't know of any update for the video card.

It seems like there is just a problem between these two vendors as I saw another EVGA user with the same problem on the same mobo. And unfortunately this is one of those bugs that is never going to get fixed.
 
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