The document explains the configuration of BIOS, detailing its functions including how it connects the CPU to various devices through the northbridge and southbridge of a chipset. It describes the role of the BIOS in system operations and introduces UEFI as an advancement over traditional BIOS, supporting larger drives and better booting capabilities. The document emphasizes the necessity of ROM for the CPU to communicate effectively with devices and highlights the evolution from BIOS to UEFI in modern systems.

1. Name: Raj Amrutiya
Roll no.92200938171
Class:1DC3
Topic: Configuration of BIOS

2. BIOS
• In this chapter, you will learn how to
• Explain the function of BIOS
• Distinguish among various CMOS setup
utility options
• Describe option ROM and device drivers

3. Necessary CPU Functions
• Two functions are necessary for devices to work:
• The CPU must have a way to talk to devices.
• Devices must have a way to send data to and receive data from the
CPU.
• Fix: We’ll elevate the MCC into the chipset and use that to
connect the CPU to all the devices.

4. BIOS
• The Northbridge is the first chip in the chipset.
• Connects the CPU to video and/or memory
• The Southbridge, the second in the chipset
• handles all inputs and outputs to the many devices in the PC and
extends data bus and address bus to all other parts of PC.
• The chipset extends the data bus to touch all the devices.
• It also extends the address bus.

5. The Northbridge and Southbridge (continued)

6. The Northbridge and Southbridge (continued)
Figure 2: The chipset extending the data bus

7. The Northbridge and Southbridge (continued)
• Figure 3: Every device in your computer connects to the address bus

8. Talking to the Keyboard
• Example: how the CPU recognizes when a key is pressed
• A keyboard controller chip (now part of the Southbridge) recognizes when
a key is pressed. Let’s say the “J” key was pressed.
• The keyboard controller scans the matrix of wires on the keyboard and
puts the scan code for the “J” key into its register.
• The keyboard controller then gets the attention of the CPU, essentially
saying, “I have some data.”
• When the CPU addresses the keyboard controller, the keyboard controller
places the data onto the external data bus so that the CPU can read it.

9. Talking to the Keyboard (continued)
• Example: how the CPU recognizes when a key is pressed
(continued)
• For all of this to work, programming has to be readily available to the CPU,
and the CPU needs this programming as soon as it is powered up—this
programming is stored in ROM.
Figure 5: Electronic view of the keyboard controller
Figure 4: A keyboard chip on a Pentium motherboard

10. BIOS (Basic Input/Output Services)
• The read-only memory (ROM) chip also called system ROM
or the ROM BIOS
• Nonvolatile (does not lose its programming, even if no power)
• Read-only means it cannot be easily erased
• Stores hundreds of programs called services; collectively, this is the
basic input/output services or system (BIOS)
• System ROM typically holds 64KB (65,536) lines of data code, though
current Flash ROM is often 2 MB or more in size
• Historically, a DIPP chip with a shiny label on it, but it has gone through
many changes

11. BIOS
• Each time the CPU needs to talk to a component, it refers to
the BIOS for the program to talk to that specific device.
• The CPU talks to the ROM BIOS the same way it talks to
RAM—through the address bus—with some of the address
bus being reserved for the ROM BIOS.
• Many devices and expansion cards have their communication
programs on ROM chips.

12. UEFI
• BIOS hasn’t changed much since it was conceived back in
the 1980s.
• BIOS works only in 16-bit mode and depends on x86-compliant
hardware.
• In addition, if there is more than one operating system loaded on a single
drive, you need one of those installed OSes to act as a boot loader.
• In 2005, Intel released its Extensible Firmware Interface (EFI)
for public standards, creating the Unified EFI forum to
manage the specification.
• Became the Unified Extensible Firmware Interface (UEFI)

13. UEFI
• UEFI acts as a super-BIOS, doing the same job in a 64-bit
environment.
• UEFI:
• Supports 32-bit or 64-bit booting
• Handles all boot-loading duties
• Is not dependent on x86 firmware
• UEFI motherboards only became available in 2011 due to
limitations of older BIOS to handle larger MBR partition
support (>2.2 TB)
• 3 TB drives had issues with older BIOS

14. UEFI (continued)
• UEFI motherboards support booting a newer type of hard drive
partitioning called GUID Partition Table (GPT)
• Supports partitions larger than 2.2 TB