Care to spill the beans on this one?
I am using a heavily upgraded cMP that started out life as a cMP 4,1 with 6 core dual processors and was upgraded to 6 core Westmere, a Saphire Radeon R580, AND an additional USB card with USB 3.0 ports (blue plastic).
I bought this computer in the upgraded 5,1 state online and was not aware of the USB card.
The original (white plastic) USB 1.0 ports are still on the cMP. I merrily plugged in my trackball, and my Apple Extended Keyboard with a Tinkerboy® adapter. All well and good.
However I plugged in a 32 Gb 3.0 USB to the USB card, blue plastic to blue plastic.
The cMP saw the USB, but the OpenCore software on bootup, did not.
I downgraded the choice of USB to a 16 Gb black plastic 2.0 USB, but still plugged it in to the USB card, black to blue. No Joy.
It was not until I realized what was probably going on that I tried the 32 Gb 2.0 black plastic, in the white plastic original ports at the back.
Bingo! We have liftoff!
I think it may have even been keeping me from
making a bootable installation disk.
So, use the original ports on your cMP (white plastic). If possible, use a 2.0, or slower USB.
I have spent the last three weeks fighting this. I am still trying to get High Sierra to install (it says there is a firmware problem) on a separate SSD.
And from what I have briefly read, it appears that upgrading Windows (I need Windows Pro) may require more knowledge than I currently have - none at all.
I would like to learn enough to not be dangerous to myself and others. Any suggestions?