On Tue, 27 Apr 2021 at 16:43, Frantisek Rysanek
<[email protected]> wrote:
>
> ITX motherboards by Gigabyte, with BayTrail and Apollo Lake ATOM, do
> have the "legacy BIOS boot" (and CSM support) available in the BIOS.

A PC BIOS is a type of program stored in a repogrammable nonvolatile
memory chip on a PC's motherboard.

Because it's a program, but ships in a chip, it's somewhere between
software (just bits and bytes, no physical existence) and hardware
(solid material object that you can kick.) So it is called "firmware",
because it's between "soft" and "hard", not quite one or the other.

A BIOS is one type of firmware. UEFI is a different type of firmware.
There are others, but not in PCs, usually.

If a computer has UEFI, it doesn't have a BIOS. If it has a BIOS, it
doesn't have UEFI.

CSM is a UEFI feature. If a machine's firmware has CSM, it must be
UEFI. If it is UEFI, it is not a BIOS. That means the computer does
not have a BIOS: it has UEFI instead.

> You can select whether to have it or not, there are several items in
> the BIOS Setup related to that.

If it has UEFI then it doesn't have a BIOS.

It is impossible to talk about the differences between BIOS and UEFI
if the terms are used interchangeably.

If I called Linux "a kind of DOS" and tried to discuss the difference
between MS-DOS, FreeDOS and Torvalds DOS we would all get very
confused and we could not effectively communicate.

So it's important to be clear and get it right. Really important. I am
not being picky about this for fun; it really matters.

Some UEFI can emulate a BIOS. Some can't.

> ITX motherboards by AsRock, with Gemini Lake ATOM: UEFI only.
> Not in the least apologetic about it :-)

> The motherboard user's guide, typically available in PDF for download
> off the vendor's website, typically has a couple screenshots of the
> BIOS SETUP. If there's not a word about a CSM or legacy boot, beware.
>
> There were some earlier examples of motherboards where the CSM
> initially wasn't available, and got added in a later version of the
> BIOS. But, I wouldn't rely on this anymore - for many vendors it's
> UEFI-only from now on.

They are probably all UEFI-only, but some have UEFI with BIOS
emulation -- that is, CSM -- and some have UEFI without.


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