DescentBB

So, I know UEFI is the successor of BIOS, and that BIOS days are counted, as it seems it won't be used anymore from 2020.

But there are still some aspects of UEFI that makes me a bit nervous, specially when using Secure and Fast Boot.
I was thinking: What would happen to an UEFI motherboard, if a Windows installation got corrupted for whatever reason, and you can't get to the actual OS, while having Fast Boot enabled?
As you can only get to UEFI options from the OS itself through Shift+Shutdown, what would happen if you can't because Windows doesn't boots at all?

When using BIOS, even if something goes wrong with your OS drive or installation, you just press Del, F2 or whatever to enter BIOS setup and can make any changes you may want (including changing boot order or something in case your OS drive got bad)

But what if your OS drive dies while using UEFI's Fast Boot, or if your boot files got corrupted (due to a problem in file system, partitions, a virus, etc), or if you take out the drive, or gets disconnected on the fly for whatever reason?
Could you still access UEFI's setup in some way without OS? Could still be reseted through the CMOS jumper procedure?
Can your Mobo even get bricked due to this type of failure?

I haven't personally to come across a Mobo that doesn't respond to some sort of keypress to jump you into the UEFI while it's going through post. I think fastboot allows it to skip a few checks, but a well timed F2 will probably still get you to where you want to be. That said, this screenshot implies some mobo's do indeed skip detecting keypresses - but it also suggests that you have to reset the CMOS to escape it if something goes wrong.
Also, some EFI's are will detect hardware changes, and force you to enter setup when something happens. At work we have a moba (an Asus strix x470-f I think?) which does exactly that. You unplug/plug a RAM stick or GPU and it'll take you to the EFI.

As a 'nix user, fighting the early EFI's were much worse than fighting the current ones.

If your Windows OS or disk somehow crashes/fails a startup, if you get a BSOD, if you shut off or reset the PC without going through a proper shut down procedure, or if you even just restart the PC then fast startup is automatically disabled and you can get into UEFI. Some implementations will even disable fast startup if you so much as unplug a USB device while the PC is off because that is considered a hardware change. Clearing CMOS would also do it. Basically there are a hundred ways to disable fast startup, to the extent that it pretty much takes real effort to actually keep fast startup working. Any event that would keep the PC from booting windows would also result in fast startup being disabled on the next attempt.

But what about situations like this one?:
http://www.h-online.com/open/news/item/ ... 01439.html

Granted, it's a specific situation that has been reported only on Samsung notebooks, and it's from early 2013, so things may have improved, but I still got some doubts about the reliability of UEFI.

Some years ago, back on 2015, I had a very bad experience while updating one of my previous computers from Windows 8.1 to Windows 10, while using UEFI (had Secure and Ultra Fast Boot enabled).
There was a crash during installation, and after that the motherboard got bricked.
However, the crash was caused by a cheap PSU malfunction.
That crash was so bad, that some sectors on the HDD where I was installing the OS got damaged and the mobo died.
I'm mostly sure the PSU is the only one to blame for the Motherboard damage, but still, since that event, I always use CSM and Legacy mode on my other computers, just in case.

On the other side, I see some advantages from UEFI that I would really like to use again (the brief period when I used Ultra Fast Boot was fabulous!), and now that CSM is about to disappear, I would like to to get used once more to the UEFI implementation, but I'm taking precautions first.

My current mobo, as you might recall from my previous thread, is from late 2013/early 2014 (can't remember its revision), a Gigabyte B85M-D3H. I'm hoping it has good UEFI support.

EDIT: Currently using UEFI with Ultra Fast Boot enabled on my computer, using the default Gigabyte OEM keys for Secure Boot.
Had to use mbr2gpt but it was pretty fast and straightforward. Everything is going smooth as for now, taking 17~ seconds to boot into Windows desktop.

Having your doubts of the reliability of UEFI is kind of pointless because you've been using it for most of the last decade already anyway. CSM and Legacy modes are just UEFI pretending to be BIOS for the benefit of older hardware/software.

A particular motherboards UEFI being buggy is the motherboard makers fault, and it isn't like old style BIOS was completely bug free. Motherboard makers are just notoriously bad at software and always have been.