Hello everyone!
I bought Sapphire Pulse Radeon RX580 8G DDR5 DUAL HDMI/DVI/DUAL DP OC W/BP (UEFI) card to replace my old Radeon HD5870 Mac edition in my Mac Pro 5.1. It has one 8 pin power socket. I made a 2x6 pin to 8 pin power cable by myself for try it at the moment. So card works in 10.13.6, it looks like "Radeon RX 580" in system setup, but it shows PCI-E speed only 2.5 Gt, and no one of 2 Display Ports work, only DVI and HDMI ports, and is a problem for my 3-monitors configuration... I tried to connect to card's DP a native DP monitor, or DVI monitor by DP to DVI dual link adapter (with additional usb power), no reaction at all. Now I replace new RX 580 with my old card, so I can not say part number from system, new card has PN 299-1E387-000SA label on it. What do you think, is it card broken, or that may be bios/framebuffer problem? Would bios flashing solve that PCI speed and DP working problems, or I have to try something else? Thank you!