Found this old article about your Mac PC with FirePro D300, D500 & D700: https://architosh.com/2013/10/the-mac-pro-so-whats-a-d300-d500-and-d700-anyway-we-have-answers/
The article mentions that the FirePro D700 is the same as AMD W9000 GPU Card:
D700
So here’s the easiest part. The D700 has exact spec matches to the FirePro W9000, AMD’s highest performing workstation-class GPU. Notable specs for both the D700 & W9000 include:
- 2048 Stream Processors (texture mapping units/unified shaders)
- 384-bit memory bus width
- 264 GB/s memory bandwidth
- 6 GB VRAM GDDR5
The W9000 specs at 4 teraflops single precision while Apple has the D700 at 3.5 teraflops. This could be because of a frequency delta for the core clock. On the W9000 it specs at 975 MHz core clock speed. Perhaps on the D700, it runs at 900? D700 is a Tahiti-based GPU.
Amazon has the FirePro W9000 at 3,158.USD. Apple is providing two D700’s in all Mac Pro configurations as options. That’s over six grand in GPU costs alone.
I don't see any Windows Bootcamp drivers for your Professional GPU Card from here: https://www.amd.com/en/support/kb/release-notes/apple-boot-camp All these Bootcamp drivers are for Consumer GPU cards.
Here is the latest W9000 AMD Driver: https://www.amd.com/en/support/professional-graphics/firepro/firepro-wx000-series/firepro-w9000
Otherwise you will need to open a Apple Ticket to see if they have an driver for your OEM Professional GPU Card.
But really the only one that can help you is AMD Moderator of Professional GPU cards @fsadough