Hey folks, i just got a very good deal on a "Sapphire Nitro+ Radeon RX 580 4GB GDDR5". I bought it in order to upgrade my Mac Pro 5.1 (Late 2009) GPU from the old crappy GT120. Unfortunately the card won't show up a boot screen. I've read some posts about the RX 580 Pulse Upgrade and hope that anyone can help me out flashing the one i recently bought. Any help would be much appreciated! Thanks in advance.