Beyond my skill set to help you with this, so sorry.I managed to start the desktop, the card is recognized, but no acceleration is working! Even video files can not be played. I used this method
IOAccelerator2D.plugin
IOAcceleratorFamily2.kext
Are you still using 10.13.4?I just thought I would let you all know I had great success with my Gigabyte RX 560 install switching from the artifacting Nvidia 650. It was truly plug and play with no flags in clover at all and no additional kexts. I can see the boot screen as well. I use a Mac Pro 5,1 SMBIOS definition with it.
I have two Dell T3500's that got one 560 each, one on a dell monitor and another on a Samsung 4k TV. I had difficulty with the DVI to DVI connection on the dell, fixed with an HDMI to DVI adaptor. The 4k monitor needed a Display Port to HDMI active adaptor to work at 4k 60 hz otherwise the HDMI works fine. I use separate audio so I did not test that.
Good luck!
I can confirm this works
See here
https://www.tonymacx86.com/threads/adding-amd-280x-graphics-card.183264/page-2#post-1183440
Are you still using 10.13.4?
Likewise!I updated to 10.13.6 and all is golden!
my motherboard with socket 775 Asus p5lp-le won’t run anything past El Capitan due to SSE 4.1 incompatiblies. I have a gt 640 in that machine. My hd 7970 is I. The z87 sabertooth machine in my signatureHello, I'm trying to run amd rx 560 on the old 775 socket, the hardware information for you, too, is the motherboard on the 775 socket, does the hd7970 work for Asus p5lp-LE in high sierra?