I purchased a XPS 8900 in April 2016 and recently added a Samsung 950 PRO SSD in the PCIe slot 4. The computer boots and works much faster than from the HDD that came installed with the machine. The issue I have is that the BIOS does not seem to recognize it as a bootable drive, only as a mass storage device.
My procedure was to create a USB with windows 10 install on it, then unplug the HDD and install the 950. I started up the machine and it booted from the USB, recognized the 950 and installed windows on it. Everything went fine and as I said the machine works. Windows disk manger recognizes the 950, has it labeled it as the “C” drive and it is in position “0”. However when I go into the bios the 950 is not listed in the UEFI boot order, when I run the BIOS diagnostic it states there is no hard drive. If I change to an unsecure boot allowing legacy ROMs the 950 shows up under the legacy ROMs but can not be booted from (I can only assume because windows installed on the 950 using UEFI). The BIOS states the computer is booting from windows boot manager, but originally when I had the HDD connected (or if I reconnect it) the BIOS reads as booting from the HDD. I should note that I did not clone the HDD, rather ran a clean install of Windows. I am not a computer expert and would like help in getting the BIOS to recognize my 950.