I have a problem... I have a Mac Pro "Eight Core" 2.8 (2008). My old graphics card "died" and I bought another one. The new card is AMD Radeon R9 270X, 4096mb. With OS X El Capitan it almost works. One monitor is working and one display port (dvi) is working, but I can´t get a picture from HDMI or any other port. This type of problem is new for me. What can I do?