I have a mid 2012 MacBook Pro, and I have done the standard mod of replacing the original HDD with a SSD and shifted the original HDD into the optical drive bay.
I then installed macOS onto the SSD and wiped the original HDD ready for Boot Camp. Now Boot Camp would not install to the HDD in the second bay, and the recommended steps from Apple was to disconnect the SSD temporarily, install Windows and then plug it back in. Worked like a charm.
Issue is not that I cannot boot into Windows. When I try to boot, I am greeted with a black screen and a blinking cursor, and that's it. Left it for a good 5 minutes and it didn't budge.
I am assuming it is because the boot loader on the primary SSD needs to have the information to boot into Windows, but since it had to be disconnected to install Windows on the second HDD this was obviously missed.
I have tried the common solution of booting into the Windows install usb, repair windows and running some
boot.exe commands to try and repair but alas it does not fix the issue.
Any suggestions? Is it even possible to have macOS and Windows on two completely separate HDD/SSDs and still boot them in parallel?