Same sound issue with MBP2011 Hi there. Have the exact same situation here: -Macbook Pro Early 2011 17" -Mac OS X 10.11.whatever -Windows 8.1 pro 64bits setup through EFI. Only way out for me was to setup rEFIND. It crashes at the end of install, but it's installed. -2 drivers issues: --6750m driver is set but not working. Since I'm to build an egpu it's not too bad (but still!) --Need to totally deactivate Intel 3000 GPU, otherwise it's black screen. When it happens, force poweroff pc, when it starts booting Windows (turning wheel) force poweroff again. At reboot, you will be prompted, and can use Safe mode where Intel GPU can be deactivated. --Audio issue. It's actually the High Definition Audio CONTROLLER (not the sound card) that has an exclamation mark in Device manager. As far as I searched on internet, there seems to be no way around the EFI-sound issue. Other solution: use bluetooth speakers or usb sound card... On the eGPU side, I was able to finally (after 3 months) see a working desktop on an external DVI screen connected to Radeon R9 (for test purpose) connected to the Thunder2 pci box. It works! And EFI is totally mandatory here (no way I could do that with legacy bios, or I missed something). If other people have experiences on Realtek/Cirrus logic issues, please state them. Best regards,