Can't get it work yet.
I can make a clean Windows 10 installation in both legacy mode and EFI mode. Bootcamp driver package can also be installed. However, for unknown reason, can't install the driver for 1080Ti. It keep saying something like "this version of OS is not supported", but I am 100% sure I downloaded the correct Window 10 64bit driver. And I tried few different version. Same result.
If I install Windows in EFI mode, leave the 1080Ti as a standard VGA adaptor (however, still nothing can display from it, which doesn't looks right), and install the Windows creator update, the cMP will not able to boot to desktop again.
Not sure if it's because my GT120 is co-exist in the cMP. I may remove it and try again later. Or it's really because Gulftown + this microcode causing the issue.
For testing purpose. I may reflash the 0087 back in and check what will happen when I go through a clean Win 10 EFI installation.
Anyway, with that broken Windows 10. That software said I am NOT protected from both Meltdown and Spectre.
Update 1: unmodded 0087 firmware shows exactly the same behaviour. Can install EFI Windows 10 Pro x64, can install Bootcamp driver package, Wifi ac / BT 4.0 can work. But can’t install Nvidia driver for the 1080Ti. Same “not compatible” warning. So, it must be something else but not microcode related.
Really no idea what’s changed. Same hardware, same SSD, same port, same Windows installation disc, same firmware... but can make the 1080Ti working in Windows in both Legacy and EFI mode (MacOS is fine).