2013 Mac Pro and macOS 10.12.4 ??

[filmak]

Boot screens not completely fixed, you still can't hold down the option key and bring up the drive picker. The monitor will stay dark if you do. The EFI Driver Version on the GPU cards has been updated though, used to be 01.00.687, now it reads 01.0D.687. I think this might be the first update of the nMP GPU EFI Driver since it was released.

Sorry, but after reading your post I gave it a try and after pressing the alt key I have the drive selection as it should be, so I really wonder why can't you see the drive selection?

 

[edanuff]

Sorry, but after reading your post I gave it a try and after pressing the alt key I have the drive selection as it should be, so I really wonder why can't you see the drive selection?

Not sure why it's not working for me. I'm using a pair of Dell P2415Q monitors. With 10.12.4, I do get the thermometer progress bar, which I did not get previously, but not if I hold down the option-key for the drive selection screen. Strange that it would work for you and not me, except maybe your Eizos are newer than the Dells.

 

[pnerd]

Not sure why it's not working for me. I'm using a pair of Dell P2415Q monitors. With 10.12.4, I do get the thermometer progress bar, which I did not get previously, but not if I hold down the option-key for the drive selection screen. Strange that it would work for you and not me, except maybe your Eizos are newer than the Dells.

On a hunch I installed the developer beta of macOS High Sierra and it updated my nMP's Boot ROM version from
MP61.0116.B25 to MP61.0116.B44. Now the option key drive picker boot screen works on my Dell P2715Q monitor. I imagine it will work on the similar Dell P2415Q. I don't know how many times I've had to boot blind and then inevitably end up in the recovery partition which takes forever to boot before I give up and plug in the HDMI cable. Plus the Dell monitor is stupidly unresponsive to it's buttons during this time -- who writes this code? That aggravation is now mostly gone. Whew.

Note I installed High Sierra to an external drive because I have not researched the implications of using High Sierra so early. You can also install to a separate partition on your main drive if you have enough space.