I am planning on putting Patriot Hellfire M.2 on a PCIex card to run operating system off of it. Has anyone done this? Does the PCIex drive present itself in the boot menu?
I will be booting Linux on it.

Is that an X58 motherboard? It won't work.
 
You need a UEFI BIOS that supports boot from NVMe, which is a fairly recent development.

arestavo
Is that an X58 motherboard? It won't work.
 
You need a UEFI BIOS that supports boot from NVMe, which is a fairly recent development.

looks like I will have to load kernel and initrd from a USB drive or other SATA disk in the system and then boot my Linux system living on the PCIex drive. Linux has native support for NVME drives, so it should work. I think I have enough SATA drives to find a 100MB partition for initrd and kernel.

I finally got this all working. Linux boots from the PCIex drive on X58 using a small grub based bootloader on a USB drive which has just the Linux kernel and the initrd.
 
The speeds I am getting with Patriot Hellfire 480GB M.2 are 1.5GB/sec sequential read and 650MB/sec sequential write, which are both very good in my books, considering X58 is limited to only 2GB/sec on x4. I am getting 3 times faster reads and 1.5 times faster writes than my earlier Crucial M500, which I moved a laptop. So, plenty happy with that. This and the memory upgrade has added about 2 more years to this OC'ed machine. I have no reason to upgrade as yet.