Hi Gary, thanks for the info. I have a Radeon 5870 now. The card offered on OWC isn't much of an advance on that one. No idea whether Mojave would work with either. I'm not going to try non-tested and non-recommended cards for this computer. I doubt I need Mojave, as I'm still happily using El Capitan.
Added to which I should say: Apple is supposed to be issuing a new MacPro at some indeterminate time. I'm sticking to what I have until I see what that is and whether it would be worth replacing this now 8 year old computer that is still doing very well.
Hi again Mark,
As mentioned previously, I will not be upgrading to Mojave until I feel comfortable that perhaps all or most of the BUGS have been repelled. It usually takes 6 -12 months for me to take the plunge, and even then I would upgrade on a Boot-Clone to test all of my most important apps before upgrading on my Main Work Drive. About 6 months ago I made a larger leap that ever before for me. On the MacPro 5,1 and Mavericks I first tried Yosemite, but then decided to go to El Capitan on another drive. El Capitan did not treat Photoshop CS6 well. The Open file Dialog could not save a resize at all, nor the Save File Dialog. I tried everything I could think of, including LuLa and the Apple Forum. The best I could get on the Apple Forum was a reply that stated that those two dialogs(windows) are governed by the OS and Apple wasn't doing much about it at all. On LuLa not many replies. I also have a MacPro 4,1 that I use for certain apps, but all of my PS work and printing to Pro Graphics printers goes is done on the MP 5,1. I will have to keep that MP 4,1 in good working order for one of my scanners, an Epson Expression 1680, a rather old workhorse that I use for scanning oversized pieces up to 20x30", but Silverfast will not support it in the 64bit Mojave OS. I use the V750 for other projects, but the 1680 has glass that's level with the surrounding bed, which makes it ideal for large pieces. I keep it in very good shape, since I do a number oversized art reproductions.
Well, I guess I sort got derailed here again, but here's another link. This is one on the Apple Forum and deals with more GPU's that are compatible with Mojave, including the one I sent previously.
https://discussions.apple.com/thread/8418863Gary