I have a 2010 Mac Pro 5,1 12-Cores 3.33Ghz, ATI Radeon HD 5770, that I recently upgraded to High Sierra from Sierra. Ever since I upgraded, I have been experiencing an issue where after boot up, 2 of the 3 displays I have hooked up will completely black out for 2 - 5 seconds and then be back up. This goes on for about 10 - 30 seconds before it "stabilizes" and stops. I checked all the display connectors to make sure that they weren't loose or anything. The weird thing with this problem is that it usually happens right after boot up and also sometimes out of nowhere it just does it. It's very unexpected.

The question here is, could this be a sign that the graphics card is going bad. I do realize that I am running the stock card (ATI Radeon HD 5770) so it might be time to upgrade it but then again, this issue never happened on Sierra.

The other question I have is, what kind of upgrades would you advice doing for this sort of machine?

Thanks in advance!