I've installed Windows 10 EFI with this Tutorial and it worked fine. But when switching from Windows to OSX using the Bootcamp "Boot to OSX..." it just rebooted into Windows again. Then I unplugged the Windows drive and it booted into OSX, but now if I choose "Windows" from System Preferences->Startup Disk it just reboots to OSX.

Is the only way of switching OS in this configuration by using a helper card and pressing alt on boot?

My current setup:

  • Mac Pro 4.1 (flashed to 5.1)
  • 2,66 Quad Xeon
  • RX480 graphics card
  • Bay 1 OSX SSD Drive
  • 2nd Optical Bay Windows SSD Drive

diskutil list

  • "Boot to OSX..." has literally never worked for me, on any of the Mac or Bootcamp setups I've used over the years. Oct 27, 2017 at 18:03

2 Answers 2


I have installed it on 2 separate drives. Windows being in EFI mode, and during the installation I did not use any Boot Camp crap, but I had to leave only 1 empty drive for Windows 10 install and boot from Windows 10 DVD in EFI mode. Then I created the Windows partition from scratch and installed Windows.

Download the bootcamp drivers from this link. I did update Windows and installed Boot Camp 6 drivers by running msiexec /i BootCamp64.msi from Administrative CMD window, which is located in Boot Camp\Drivers\Apple directory. Then I connected all the other drives.

In macOS High Sierra I installed Boot Runner from Twocanoes. From the recovery partition's terminal I executed:

csrutil enable --without nvram

so the Boot runner can boot Windows. After logging back into macOS High Sierra, logout. You will come to the Boot runner's startup disk screen. Select Windows and it will reboot to Windows. If you want to go back to macOS, select macOS High Sierra option in the startup disk of the Boot Camp manager (in Windows)

I have migrated my internal Windows drive to Sonnet Tempo SSD Pro Plus SATA III PCI Express Card. Unfortunately, due to the fact the drives on this card are recognized as external, I guess Boot Runner does not populate an option to boot directly from this drive. As a workaround though I can select the SSD as a boot drive from the Boot Camp manager in my internal Windows drive which works like a charm.


i pretty much have the exact same problem with similar configuration.

Windows 10 is working fine but "set startup disk" in system preferences seams to not work… In System Preferences under startup disk it shows up my windows 10 folder correctly but it doesn't work when selected and restart – it boots just in Mac OS again.

when i boot with holding option(alt) (Mac startup manager) to select the startup disk it shows up "EFI Boot" instead of "Windows" but works actually fine when boot into "EFI Boot" (which is my Win10 install).

My guess is (when you look at diskutil list) that the EFI Partition should be in position 1 instead 2 (should be disk3s1 instead of disk3s2) to work correctly – Windows Recovery is set on disk3s1 falsely.

Because i use a unflashed GTX 1070 GPU with Nvidia web drivers i'm not able to navigate to the startup manager holding option(alt). For that reason i use bootchamp now to boot in to windows manually. only downside of this method is that i have to boot into mac OS first every time and when restarting the computer from windows it boots up in mac OS again because Bootchamp only sets the startup disk to windows for once. (But this isn't actually a problem for me because i use Mac OS more)

i hope you could find any solution already or i could help you a little bit with your/our problem


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