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I keep hearing the term “Enter BIOS Setup”. But when talking about BIOS we also have another low level software call UEFI.

This is confusing because in the setup screen we can choose between BIOS and UEFI

  1. Is the modern good looking Setup GUI part of UEFI? If so then can we also access the simple text setup screen as BIOS mode?

  2. Who is responsible for setup screen? Bios or UEFI?

  3. And what is the correct way to call the setup screen? “Enter bios setup”, enter “UEFI setup”?

2 Answers 2

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"Firmware setup" would be the most general term.

UEFI is a standard specification that defines how PC firmware should behave and what features it should provide to the bootloader and to the OS. Most PCs now have firmware that's compatible with the UEFI specification.

Before UEFI, most PCs had firmware that was roughly compatible with the original IBM PC BIOS (though it had been extended in various ways, e.g. adding ACPI). So the term "BIOS" has the broad meaning of "main PC firmware" in general, and a more specific meaning of "firmware compatible with the original IBM PC BIOS", although the latter is much more common.

The two aren't mutually exclusive – the same firmware can provide both UEFI and IBM PC BIOS features at the same time.

This is confusing because in the setup screen we can choose between BIOS and UEFI

In most cases, what you're really choosing here is which boot methods the firmware will provide. The actual firmware doesn't change at all – it's still UEFI firmware – usually you're just enabling or disabling the "BIOS compatibility module".

Is the modern good looking Setup GUI part of UEFI? If so then can we also access the simple text setup screen as BIOS mode?

Firmwares built to the UEFI standard are far more likely to have a "modern, good looking setup GUI"... but that's not a guarantee. Plenty of older UEFI firmwares had a text-mode setup screen. But on the other hand, some PCs had graphical setup screens in the 1990s.

Regardless, if you have UEFI firmware, then yes, its setup UI runs as an UEFI application. Even if you switch the OS boot mode to "BIOS only" or "legacy only", this doesn't affect the firmware itself – it still has the same functionality available to its internal components, just not exposed to the OS anymore. Because of that, usually there isn't an alternative simple text setup screen.

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  • Thank you! 1) is the BIOS only and legacy only the same thing? 2) Is BIOS compatibility module the same thing as CSM support? So when we update modern mother board BIOS we are actually updating UEFI firmware, the term bios used here is actually incorrect?
    – Zanko
    May 23 at 9:08
  • asus.com/support/FAQ/1038568 The term Update Bios in this case is technically wrong?
    – Zanko
    May 23 at 9:10
  • 1. No. BIOS is just BIOS. Legacy only in UEFI often means disabling modern efi boot and enable SHIMs to support old boot methods. 2. Yes, Updating BIOS means updating the UEFI firmware.
    – Hennes
    May 23 at 9:16
  • 1) Yes, in the context of PC firmwares, "legacy" or "legacy boot" now usually refers to BIOS boot mode. 2) Yes, "CSM" (Compatibility Support Module) is the official UEFI terminology (I think). 3) Personally I wouldn't say it is fully incorrect – you could accept that the term "BIOS" can also refer to the system firmware in general and not just strictly to IBM PC BIOS (e.g. many game consoles used to use the same term even though they had nothing to do with PCs). Many people are better familiar with the term "BIOS" than "firmware", so when the page says "update BIOS" they know what it means.
    – user1686
    May 23 at 9:16
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hen a computer boots it runs its firmware.

There are different kinds of firmware. Dozens across platforms, but for PC compatibles their are two big flavours:

  1. Firmware compatible with the IBM PCs (1984, 4.77Mhz) Basic Input Output system
    A.k.a. BIOS.
  2. Firmware from the last decade using EUFI.

EUFI is used in any PC from the last decade. They no longer have a BIOS. Period.

But confusingly enough the EUFI firmware still displays 'Press F12' or 'Press DEL' to enter BIOS. I think they do it because people are used to the setups screen to be called BIOS, but it is technicaly incorrect.

A second confusing part are the compatability SHIMs in some EUFI implementations, which make the UEFI firmware compatible with a BIOS firmware. At that stage it often looks like BIOS, feels like BIOS, acts like BIOS,.... but behind the covers it still is EUFI.

Ok, enough of the introduction, lets answer the specific questions:

1. Is the modern good looking Setup GUI part of EUFI? 

It can be either. Early BIOS was text only, but near its end there also were graphical BIOS implementations. Same with UEFI, some of them have pure text, some graphics.

It seems to be more capability related (read: more modern faster computers) which decides if you get a text interface, or a graphical interface.

2. Who is responsible for setup screen? BIOS or EUFI?

The firmware. Which on old PCs is BIOS and on new PCs is EUFI

3. And what is the correct way to call the setup screen? 
   “Enter bios setup”, enter “UEFI setup”?

I would go for 'enter setup' (and then start EUFI, or coreboot, or BIOS, or ...<

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  • Thank you for detailed answer cleared up a lot of confusion. By EUFI you mean UEFI?
    – Zanko
    May 23 at 9:23
  • Yes. I will correct.
    – Hennes
    May 23 at 9:29
  • I’m addition, what does (BIOS Type: 256MB UEFI) refer to when looking at mother board? The firmware size is 256MB?
    – Zanko
    May 23 at 10:44
  • There probably is a EEPROM on the motherboard which contains the firmware. I have no idea how large those are these days, but 1megabit (bit, so 256 kiloByte) certainly seems to be the right order of magnitude. Then ofcourse there is the EFI system partition. The firmware loads configurations and possibly drivers from there. That typically is 100Mb (win7) or larger. The first is on a chip on the moterboard, the second is on a drive. (HDD, SSD, ...)). Can you add a direct link to the 256MB part?
    – Hennes
    May 23 at 11:23
  • supermicro.com/en/products/motherboard/X11DDW-L Can find it under system bios section
    – Zanko
    May 23 at 13:18

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