The Basic Input Output System (BIOS) and Unified Extensible Firmware Interface (UEFI) are firmware interfaces that determine how a computer starts up.
They work as a mediator between the hardware of your system and the software installed on it by initializing, configuring, and testing each device attached to your computer.
With technological advancements in recent years, EFI technology has replaced BIOS in modern systems providing better security features like Secure Boot Mode.
Despite knowing this, I find it entertaining to walk down memory lane to remind myself of just how far technology has come.
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So let this short article serve as an abbreviated overview of the technology.
UEFI (Unified Extensible Firmware Interface) was developed to overcome the limitations of legacy BIOS, which operated in GUI-less 16-bit real mode, restricted hard drives to 2 terabytes, and provided for a maximum of 4 partitions.
And according to Intel, the BIOS was killed off in 2020.
UEFI is newer and more capable, having been developed in 2004 by Intel, whereas BIOS was developed in the 1970s by Gary Kildall of Digital Research, Inc.
BIOS: Basic Input Output System
The BIOS is firmware, a computer program that’s embedded (and thus pre-installed) in a hardware device. It’s built into the motherboard and initializes the computer’s hardware after conducting a power-on-self-test, also known as a POST.
The BIOS then searches for a bootable device to continue the loading of an operating system.
BIOS is a legacy standard built in the 1970s for older computers during a time that didn’t imagine modern technology.
UEFI: Unified Extensible Firmware Interface
A traditional BIOS uses a 16-bit processor mode and works with an MBR (a Master Boot Record), while UEFI uses a 32/64-bit processor mode and works with a GPT (a GUID Partition Table).
A GUID (Globally Unique Identifier) is a 128-bit number used to identify information in computer systems. It’s commonly used to uniquely identify items such as files, directories, and registry keys, and for network communication. GUIDs are composed of 32 hexadecimal digits and are typically represented in the form of 8-4-4-4-12 characters. E.g., 78D3CF3E-6E9A-4583-9B8B-E0C6A7FB0D67
UEFI also provides more advanced features such as secure boot, a graphical user interface, faster boot times, and support for larger hard drives and more partitions.
If you’re concerned about security in earnest, ensure you’re using the more modern UEFI method of booting your computer, as a secure boot is an important security control. In other words, this ensures you’re only booting from software trusted by the manufacturer.
Frankly, this shouldn’t be hard to do as no modern computer boots from BIOS, but there is indeed some legacy hardware still out there. If this is you, maybe it’s time to retire it.
BIOS, CMOS, UEFI — What’s the Difference? (Video)
"Amateurs hack systems, professionals hack people."
-- Bruce Schneier, a renown computer security professional