Hello Nando,
I'm trying to set up GTX 970 with my mac mini 2012 and AKiTiO Thunder2 PCIe box. I tried DSDT override on bootcamp Windows 7 and I'm able to see the large memory, but unable to get rid of error 12.
Do you think the setup 1.3 will help? I see no one mentioning mac mini nor AKiTiO PCIe box in this topic, so I'm not feeling confident. BTW, . The GTX 970 is recognized as connected to "Xeon(R) processor E3-1200 v2/3rd Gen Core processor PCI Express Root Port", while all the onboard root ports are series 7 pcie.