Quiz 4: BIOS & UEFI

Question 1

List 8 Major Advantages of UEFI

Answer 1

• Boot mode – has a secure boot feature which provides better security and faster boot times
• Drives – Can support drives larger than 2.2 TB because it uses a GPT partition scheme
• Drivers – UEFI allows for bigger drivers and supports discrete drivers which can be loaded at runtime and updated without updating the whole firmware.
• GUI – more modern interface which enables new modules and USB devices to be added easier
• Multiple OS support – BIOS allows only one OS, but UEFI lets you install loaders for most operating systems (e.g. Windows, Linux)
• Programming language – written in C which allows for more features, is easier to understand, and enables users to add and remove instructions more easily.
• Modular design – allows for faster and more efficient development, modification, debugging and customization of the firmware
• Backward and forward compatibility – can run old BIOS code which makes it compatible with older computers or drives, and can adapt to new hardware and updates easily.

Question 2

Define each of the (BIOS and UEFI)? Elaborate why UEFI replace BIOS?

Answer 2

BIOS is software which was used by all computers in running the boot-up process: It performs self-tests and checks (POST) and it loads the operating system and performs self-tests and checks to make sure everything is working properly.

UEFI is the more modern software used for boot-up. It does the same things as BIOS in a much more efficient and modern way.

UEFI ultimately replaced BIOS because:
UEFI supports GPT and does not rely on the minimal space available for a boot code
✓ UEFI is extendable and supports a binary format to execute programs directly in the firmware, pre-OS (i.e. updaters, network tools, troubleshooting tools)
✓ UEFI includes support for Secure Boot, a cryptographical protection against tampering

Question 3

8 Steps of Bios Startup

Answer 3

1. Power-On or Reset:
   When you turn on your computer or perform a reset, the CPU (Central Processing Unit) starts executing instructions from a predefined memory location, known as the reset vector.
   The reset vector is usually located at a fixed address in the system’s memory, and it points to the beginning of the BIOS firmware.
2. BIOS Initialization:
   The CPU begins executing instructions from the BIOS firmware stored in a non-volatile memory chip (typically a flash ROM) on the motherboard.
   The BIOS firmware runs a Power-On Self-Test (POST) routine to check the hardware components (CPU, RAM, motherboard, etc.) for errors. Any detected issues are reported through a series of beep codes or displayed on the screen.
3. System Setup (CMOS/UEFI):
   The BIOS firmware reads configuration settings stored in a special memory chip called CMOS (Complementary Metal-Oxide-Semiconductor) or UEFI (Unified Extensible Firmware Interface) settings, depending on the system.
   These settings contain critical information about hardware settings, including the boot order, date and time, and various system preferences.
4. Boot Device Selection:
   The BIOS checks the boot order settings to determine from which device to load the operating system. Common boot devices include the hard drive, SSD, optical drive (CD/DVD), USB drive, and network.
   If the first boot device is not available, the BIOS will proceed to the next device in the boot order until it finds a valid bootable device or exhausts all options.
5. Loading the Boot Loader:
   Once the BIOS determines the boot device, it reads the Master Boot Record (MBR) or the GUID Partition Table (GPT) from the selected device. The MBR or GPT contains information about the partition structure and the location of the boot loader.
   The BIOS then loads the boot loader (e.g., GRUB, Windows Boot Manager) into memory from the specified location on the boot device.
6. Boot Loader Execution:
   The boot loader is responsible for loading the operating system kernel and initiating the boot process.
   Depending on the boot loader and the operating system, the boot loader may present a menu to select an operating system or kernel configuration if multiple options are available.
7. Operating System Initialization:
   Once the boot loader hands control over to the operating system, the OS kernel takes charge.
   The kernel initializes device drivers, sets up the file system, and starts essential system processes.
   Finally, the graphical user interface (GUI) or command-line interface (CLI) is presented to the user.
8. User Login:
   If required, the user is prompted to log in to the operating system.
   After successful login, the user gains access to the desktop or command-line environment.

Question 4

Disk Partitioning

Answer 4

Hard drives are physically divided into sectors (512 – 4k
bytes). To give a logical structure to a hard drive we can
divide the drive into partitions.

❖The following partioning styles are common:
❖MBR (Master Boot Record)
❖GUID Partition Table (GPT)

Question 5

MBR (Master Boot Record)

Answer 5

Has a 446 byte writeable boot section
❖ Supports up to 4 bootable partitions
❖ More partitions can be added through extended partitions (uses one physical
partition)
❖ Maximum disk size is 2TB due to the 32-bit partition address
❖ Limitations? All of the above.

Question 6

GPT (GUID Partition Table)

Answer 6

A different partitioning style without the MBR limitations
❖ 128 partitions
❖ “Unlimited” disk size (18EB)
❖ Backwards compatibility for MBR-style boot code

Question 7

UEFI: Secure Boot

Answer 7

The UEFI 2.2 specification adds a protocol known as secure boot, which can secure the boot process by preventing the loading of drivers or OS loaders that are not signed with an acceptable digital signature (Ex.MSCA).
❖ “Secure Boot” is an optional module that resides inside and is part of the
“UEFI”.
❖ The “Secure Boot” module of the UEFI can be enabled or disabled by the
computer user at any time before or after the operating system is installed
into the computer.