I have a 2009 Mac Pro 4,1 Quad Core 2.66 (without 5,1 firmware upgrade) running 10.10. I've been afraid to upgrade in fear of compatibility issues with my current set-up. Now it's hard to get anything new due to this old OS. What is the latest version of Mac OS that can support that platform? And how would I get it?
Also, is there a way to equip this 4,1 with more than 32gb ram? (I attempted booting in 64bit but it didn't read extra ram sticks)