@sinbad before Windows doesn't necessarily mean before Microsoft code though. As far as I understand it, UEFI is fast because rather than probing the drives for an MBR and handing over to that, it just executes an EFI at a pre-configured location but the actual EFI can be anything. I mean... Obviously its purpose is to spin up everything else and hand over to the 'real' O/S, but programmatically it's just an executable like anything else. So if Windows dumps its own EFI for boot, it gets control