According to the documentation and specs, they'd have you believe that the original B450 Tomahawk was NVMe compatible right out of the box. I'd last updated my BIOS to version 7C02v17, and Live Update said that was all I needed as I'm running a Ryzen 5 2600.

So yesterday I get my hands on an SK Hynix Gold P31. Take out the old SATA WD Blue 3D I'd been using for the last couple of years. Fire up the system and... nothing. Just a black screen. Can't even get to the BIOS. I plug in the thumb drive for installing Windows. Nothing. As long as the SK drive is in the M.2 slot, all I get is a boot fail LED and a blank screen. The WD drive boots fine when it's plugged back in. Clearing CMOS on the off chance the security measures didn't like the new drive didn't do anything.

I made sure the new drive was working with a USB enclosure I'd bought and (eventually, but that's another rant) cloned the boot drive. Still no joy when the new drive was in the M.2 slot.

So finally I decide I've got nothing left to lose and update the BIOS for the first time in years. Updated to 7C02v1E. Lo and behold, the SK is recognized! The first attempt at a boot BSOD'd, but it wasn't just sitting there looking stupid any longer. Time for a fresh install on a speedy new drive! That's done, and here I am. The numbers don't lie.

tl;dr: Even if you're running an older CPU, check your BIOS if your fancy new piece of kit brings your system to a screeching halt as soon as you plug it in.