Pegasus3 On iMac Pro (2017) Will Not Allow Me to Boot Into Windows10 via Bootcamp

  • Last Post 18 November 2020
Thomas Wheeler posted this 16 November 2020

I have an iMac Pro (2017) running Big Sur with a Pegasus3 R6 Thunderbolt 3 configured for Raid 5 attached.  i am running under Big Sur. I have the latest versions of both firmware and Promise Utilities software installed. As long as the Pegasus3 is attached to my iMac Pro I am unable to boot into windows by holding down the option key and slecting the Bootcamp volume. The Windows logo appears and then a spinning circle of white dots appears and spins forever without completing bootup. If I disconnect the Pegasus3 R6 system from my iMac Pro and go through the same procedure for booting into Windows 10, the bootup occurs promptly and without any problems. Clearly there is some negative interaction between the Pegaus3 R6 and booting into Windows 10 via Bootcamp. This probllem of booting into Windows 10 with the Pegasus3 R6 attached did not suddenly occur after installing Big Sur on my iMac Pro.  Under the previous two Mac OS operating systems on this iMac Pro I have not been able to boot into Windows 10 via Bootcamp with the Pegasus3 attached. Note also yhat I have a Mac Pro (2019) with two Pegasus2 R6 units attached and there I am able to boot into Windows 10 via Bootcamp with no problem.The issue is specifically with the Pegasus3 R6 attached to the iMac Pro. 

Can anyone suggest a solution to this issue.?   Thank you in advance for responding. 


Thomas Wheeler posted this 18 November 2020

I am disappointed that after two days there has been no resonse to the issue of my iMac Pro not booting into Windows with the Pegasus3 R6 attached. Does anyone from Promise Technology even monitor these forums?

I filed a support ticket on this issue wiith Promise Support two years ago and spent several months with their support only to be told that there was nothing they can do. I had hoped that some technially knowledgeable individual reading this forum ccould offer a solution.

Let me further add that I have disabled all security options on the Apple T2 chip in this iMac Pro but that does not resolve the issue. i work in windows frequently doing 3D animation and modeling and having to disconnect my Pegasus3 R6 in order to boot and then reconnect is a real pain.  

Again, I thank anyone in advance for responding.