Hi, I have a MacPro 4,1 flashed to a 5,1 running High Sierra, and I swapped in a mac version of the Radeon 4870 512M, that is known good. Strangely this card works but does't seem to have accelerated drivers or 3D? This is surprising to me as it has been plug and play in my MacPr 3,1 for many OS iterations. Any ideas on why this might not work or be supported? Thanks in advance.