How does UEFI even work?

[fuzzybabybunny]

All I know is that UEFI replaces a motherboard's BIOS, and I totally don't get how that's possible.

From what I know, the BIOS is basically your motherboard's firmware. It's like a little operating system that resides on your motherboard's ROM.

You can have literally NOTHING else installed on any disks but you will always have your BIOS to "boot" into. The BIOS is OS-agnostic. It doesn't care if you have Windows or Linux or whatever. After the BIOS is loaded it tells the motherboard which drive to actually boot from (USB, SATA, etc).

So what's this UEFI thing? How the hell is there a Microsoft product now replacing the BIOS? And what are the repercussions of this if I were to try and dual-boot a Linux distro or if I was originally dual-booting a Win7/Linux system and then did an in-place upgrade to a Win10/Linux system?

 

[Puffnstuff]

Unified extensible firmware interface is a new way for the bios and hardware to communicate and is much more adaptable than efi alone. A uefi bios and the os work together and when you perform a uefi installation of windows it allows it to operate at the most efficient level it can which is why uefi systems boot so fast with a ssd. Windows 8 was their first os to integrate with the bios. Windows 7 would do a uefi install but it wasn't able to integrate like 8+. I only perform uefi windows installations on my pc's for the best performance.

 

[fuzzybabybunny]

So UEFI does NOT replace the motherboard's own BIOS, right?

Does a motherboard's ROM / BIOS have to first be updated to support UEFI?

If the motherboard does not support UEFI, Windows 8/10 will still install fine, right?

If you're booting from a USB stick, does that USB stick have to first support UEFI booting? So older USB sticks may no longer work?

 

[Auric]

UEFI generally include a Compatibility Support Module (CSM) option which essentially acts like a traditional BIOS with the modern GUI -which is arguably preferred to avoid limitations.

https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface

 

[SparkyJJO]

Think of UEFI is like bios 2.0. So yes, it "replaces" bios 1.0, although they are still (typically) backwards compatible, including legacy booting non UEFI operating systems/USB sticks/etc. Exceptions are some pre built boxes from Dell, HP, etc. You don't need UEFI to install 8 or 10.

I don't have UEFI on my old Z68 board.

 

[bigi]

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enjoy. strippoker