I bet this has been discussed already but I can't find it by searching so sorry for probably an answered question. I have MacPro (Early 2009) - MacPro4,1 which according to Apple's list will not run Sierra. It requires MacPro5,1 (Mod 2010.) But from all I have read MacPro4,1 is almost identical MacPro5,1 which does run Sierra. As it turns out I have mine tricked out with 20Gig of memory and an ssd and I'd love to keep using it as it runs great. I understand there's a way to make mine look like a MacPro5,1 and it's pretty easy. But I can't find instructions that look trustworthy. Can someone here help me? Thanks!