Query about Samsung 950 Pro M2

I have just finished my build and I am a bit concerned that I am not getting the best out of my 950 Pro M2 SSD.

When I installed Windows 10, the drive still shows up as MBR and when I try and format it as GOT using diskpart command, it does not "take".

I tried disabling CSM on the motherboard (Rampage V Edition 10) and I was left with no boot devices at all (I cannot see an easy way to force UEFI).

The M2 boot time takes around 10-15 seconds, is this normal or should I be getting sub 5 second boots?

I faced a similar problem using a Samsung 850 Pro 1TB SSD whilst trying to do a clean installation of Windows 10 Pro 64-bit.

This is what finally worked for me.

During installation of Windows 10, when you reach the first screen where you're asked to select your desired language, keyboard etc, hit Shift + F10. This will bring up a command prompt.

Type the following commands:

diskpart
list disk
select disk 0 (0 being the disk you wish to install Windows OS to)
clean (this deletes all partitions)
convert GPT (this initializes the disk as GPT)
exit
exit

Continue with the installation.

Hope of some help.

You need a sub 4gb iso that you can put onto a USB stick with fat32/fat32(large) and GPT scheme selected. I use Rufus.

my R5E has CSM disabled/secure boot on and installs fine. Bootup is about 5-8 seconds with fast boot working (it doesn't always and takes 10 seconds then, after the BIOS has finished faffing around.