Windows 2012 R2 Black Screen

[NiKiZe]

Replied to your other message in that other thread.
Could you post the iPXE script that you are using to start wimboot?

since bootmgr.exe is used I'm assuming PCBIOS mode and not EFI
Test with less then 4GB of ram and see if it gives any difference.
Also try adding the gui option on the wimboot line.

Some combinations of windows and hw will not work without the gui option, while it in most cases is easier to debug issues without the gui option.