Difference between UEFI and BIOS architecture

Question

How does the UEFI offer an advantage over BIOS architecture?

Why is it so difficult install Linux(read Ubuntu) as a dual boot option on a UEFI Windows 8/8.1 PC? I say it's difficult because of this guide on Ubuntu help.

Answer 1

The major advantages that UEFI provides are:
1. Better disk support: UEFI supports GPT (GUID Partitioned Table), which adds support for very large hard drives (e.g. those in excess of 2TB.). BIOS uses MBR, which had a size limitation of 2TB because of 32bit tables. UEFI has 64bit tables allowing the boot devices to be larger than 2TB. This has a lot of advantages in the longer run.
2. Bootloaders no longer needed: This is the mechanism the UEFI spec provides for operating systems to make themselves available for booting: the operating system is intended to install a bootloader which loads the OS kernel and so on to an EFI system partition, and add an entry to the UEFI boot manager configuration with a name – obviously, this will usually be derived from the operating system’s name – and the location of the bootloader (in EFI executable format) that is intended for loading that operating system.
3. Added features: UEFI has added support to the following features which were not available with BIOS

• cryptography
• network authentication
• support for extensions stored on non-volatile media
• an integrated boot manager
• shell environment for running other EFI applications such as diagnostic utilities or flash updates.

4. Better interface: UEFI was designed with more room so as to accommodate graphics, thus facilitating a neat GUI.
5. Faster boot-up.

Regarding the Linux difficulty you mentioned, It was initially because many Windows 8 PCs shipped back then were not allowed to turn off secure boot. Secure boot was something that wouldn't allow an OS to boot without a PKI certificate, which had to be added to the UEFI's list. This was later resolved.

Sources: ExtremeTech, UEFI booting, PCMag UEFI article, uefi vs bios

Answer 2

These are in fact 2 questions in one, so here are my answers:

1. UEFI offers more flexibility in boot and device management in a system, it allows the use of GPT disks that remove the limit of 4 primary hard drive partitions, allows the choice of operating system to be booted from the firmware, enables the use of signed bootloaders to improve protection against malware, and the option for configuration backup and restore.
2. There are several reasons that installing Linux on a UEFI Windows computer is more complex, the primary one is that some Windows computers test the signed bootloader by default and there are several computers that even disallow the boot of unsigned loaders completely, another issue is because Windows starts loading as the boot options are displayed, so if you want to start Linux instead of Windows, you'll have to reboot if you choose that from the Windows boot menu and Windows does not add the Ubuntu option automatically, in addition, Windows often provides methods to fix boot issues that sometimes overwrite the work done by the Ubuntu installer since it does not identify the boot loader.