Hey guys,

Can't figure this thing out. I have a msi b450i motherboard and 2 seperate ssd's one containst Windows 10 the other contains Arch Linux. CSM is disabled and so is secure boot. I manually disabled hibernation in Windows.

Windows + bootmgr /sdb (EFI | GPT)
Linux + grub /sda (EFI | GPT)

Motherboard allows me to select UEFI: Windows by default.
Motherboard does not allow me to select Linux by default (not listed).

I can override the bootsequence and boot into grub. Both Linux and Windows start up as expected out of grub.

I'm so puzzled.. Really don't know how to solve this.

Try installing refind as your boot manager.

Thanks, I had previously tried this with syslinux instead of grub2. Because I didn't have any succes I decided to go with another bootloader. Grub2 has supposedly has the most/best support, so I'm kind of hoping it can be done within grub. Will keep this option open for another time if I can't fix it.

rockhopper_penguin,

Refer to page 45 of the MSI B450i manual, enter the BIOS and select [LEGACY+UEFI] boot mode.

Manual:
https://download.msi.com/archive/mnu.../E7A40v2.2.pdf

See extract below.

Boot

Boot Mode Select [LEGACY+UEFI] Sets the system boot mode from legacy or UEFI architecture depending on OS installation requirement.
This item will become un-selectable and will be configured automatically by BIOS when Windows 10 WHQL Support is enabled.

[UEFI] Enables UEFI BIOS boot mode support only.

***[LEGACY+UEFI] Enables both Legacy BIOS boot mode and UEFI BIOS boot mode.

Secure Boot can be disabled but Legacy/CSM needs to be enabled.

I had actually tried that before and also read about it. It did not work. Then it hit me that the bios needs to completely reload before the settings can be adjusted. I.e. I needed to enable CSM then reboot to populate the bios priorities, only then I was able to select Arch and prioritize it over Windows. You pointed me in the right direction at least, so I thank you all for your replies. This is now solved as fas as I'm concerned.