I should have done more research before buying this card. It has not arrived yet. But I see lots of problems people have had putting GTX 280 on a CMP running Catalina. Dang. When I try the installation, i will post what happens.
If you get the genuine Mac version of the GTX 680, it works perfectly. There are lots of PC versions out there that have been flashed by the user, but don't always work as expected. Mainly, you don't get an image until your Mac gets to the desktop, and you can't do an Option key startup (because there's no image to see what you're doing).
I had one in the same model Mac. It worked as expected. You don't need to install any drivers. The OS supports the true Mac version directly.
What exact GTX 680 model did you buy?
I personally wouldn't worry, it'll work.
For bootscreen you have different options nowerdays (GTX 680 Mac ROM flash or better - update GTX 680 GOP and flash EnableGOP to your Mac Pro).
I've used a lowley GTX 650 with macOS Catalina for years in my 5,1 doing music production.
View attachment 2388845
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View attachment 2388848 Condition
Used
Seller Notes
“Excellent working condition. Apple EFI Boot Screen, 4K output, Metal macOS 10.14 Mojave, 10.15 ... Read moreabout the seller notes
Brand
EVGA
Chipset Manufacturer
NVIDIA
Chipset/GPU Model
GeForce GTX 680
Memory Size
2GB
Memory Type
GDDR5
Features
Apple EFI Boot Screen, Metal Support, 4K Output, macOS 10.14 Mojave, macOS 10.15 Catalina, macOS 11 Big Sur, macOS 12 Monterey, macOS 13 Ventura, macOS 14 Sonoma, Mac Pro 2008 3,1, Mac Pro 2009 4,1, Mac Pro 2010 5,1, Mac Pro 2012 5,1, NVIDIA Kepler, GT 630, GTX 680, GTX 780, GTX Titan, MacVidCards MVC Compatible
Connectors
1x HDMI, 1x DisplayPort, 2x DVI
Compatible Slot
PCI Express 2.0 x16 (Mac Pro)
MPN
02G-P4-2683-KR
Power Cable Requirement
6-Pin + 8-Pin PCI-E
APIs
Apple Metal, CUDA, OpenCL, OpenGL
Cooling Component Included
Fan with Heatsink
Country/Region of Manufacture
China
Item Height
4.376 in - 111.15 mm
Item Length
10.5 in - 266.7 mm
Item Width
Dual Slot