As I found out when I went to download Sierra, my Mac Pro has been dropped from the list of Macs that will run Sierra. I have read here in the various forums that the Mac Pro can be "Flashed" with a newer software. As far as I can tell my Mac Pro is also known as a 4,1 and I guess it can be flashed with 5,1 software. I have upgraded the CPUs to two 3.32 GHz Quad Core Xeon CPU's, and I currently have 24 GB of Ram. I have three NVIDIA GeForce GT 120 512MB graphics cards of which I cam using one with two monitors. My question is this; Would flashing my Early 2009 Mac Pro with 5,1 software make it qualify to run Sierra? Would the flashing make it appear as a 2010 or maybe a 2012 Mac Pro? I think I can find a thread that explains how to flash the Mac Pro and probably a link to the 5,1 software, but I have not been able to determine why I would want to, unless it allows me to load Sierra, and then I would attempt it. I am also trying to find information on Graphics cards for this Mac Pro, I assume there are better alternatives to the current ones I am using.