System setup:
nmp late 2013, D700x2 GPUs, 20 Go RAM,
MacOSX Sierra, Windows 10 Anniversary edition under Bootcamp
eGPU setup:
Sonnet echo express III
EVGA NVIDIA GForce GTX 970, 4 Go
On the mac side, eGPU was installed without a glitch by running "automate-eGPU.sh".
Under Bootcamp, the GTX 970 appeared in Device manager, but with the dreadful "error 12".
Since eGPU-setup 1.20 or 1.30 cannot be used on Bootcamp GTP partitions, I first used the DSDT override method described in Techinferno forums,to extend the root bridge into 36-bit space, which indeed created a large memory entry in Device Manager, but was without effect on "error 12".
Then, with the kind help of *********, I used the method based upon Creating a textfile called "startup.nsh" in EFI root to enable VGA Output on the PCI bridge connected to my Thunderbolt ports
(https://www.techinferno.com/index.php?/forums/topic/1843-2012-15-rmbp-gt650m-gtx560ti8gbps-tb1-th05-win81-shelltoe/).
However, even after finding the adresses of AMD and Nvidia GPUs and testing number of modifications of memory's entries (eg mm 0001013E;PCI :8 in the example od Sheltoe), error 12 was still present.
With the kind help of *********, I also tried to disable and then re-enable Nvidia card as well as, one by one, the 5 PCI brige entries above it in Device Manager/Devices by connections, but here again without succeeding to eradicate error 12.
Finally, I tried the app "automate -eGPU EFI" developed by euqlaog (https://www.techinferno.com/index.php?/forums/topic/10057-automate-egpu-efi-mac-bootscreen-on-egpu/). However, probably because I only had access to the demo version, the app did never let me to boot either in windows or in macosx.
So far,I am therefore stuck in the middle of nowhere. Since Apple has visibly no plan to upgrade nmp in a near future, I am pretty sure that number of nmp owners would be, as I am, very interested in getting a reliable way to get eGPU working under Boocamp. Indeed, nmp is still a very efficient computer, except for AMD GPUs which are now clearly outdated. So, if anyone has the solution, that would be great...