1. BIOS
Chapter 6

2. CPU Communication with the System
The CPU needs to communicate with all components of the computer system
The Northbridge chip/circuitry controls the high speed communication channels
RAM
Video
The Southbridge chip/circuitry controls the low speed communication channels. Input/Output Controller Hub (ICH)
Keyboard
USB
Disk drives

3. BIOS Basic Input/Output Services
Contains programs to allow CPU to interact with the system before the operating system is loaded
Stored in ROM
ROM - Read Only Memory
PROM - Programmable Read Only Memory
EPROM - Erasable Programmable Read Only Memory
EEPROM - Electrically Erasable Programmable Read Only Memory
Flash ROM
Firmware

4. CMOS Complementary Metal-Oxide Semiconductor
Holds data about connected devices to be used by the BIOS programs
Also acts as the clock
Modify CMOS
Every computer has a system setup program that can be accessed at boot time

5. Tour through CMOS Setup Program
MB Intelligent Tweaker
Can change the voltage and multiplier settings for the CPU
Advanced BIOS Features
Covers a variety of settings such as boot devices and order
Virtualization Support
Hardware support for a virtual machine
Chassis Intrusion Detection
Advanced Chipset Features

6. Tour through CMOS Setup Program
Integrated Peripherals
Configure, enable, and disable onboard devices
Power Management Setup
Control how and when devices turn off and on to conserve power
Overclocking
PnP/PCI Configurations
Rarely used
Trusted Platform Module

7. Option ROM and Device Drivers
BIOS programs must be available for all devices attached to the computer system
Option ROM
ROM chip is on the device controller
Device Drivers
Software file
Programs are loaded into RAM

8. Power On Self Test (POST)
The Beep Codes
Text Errors
Occur after video has passed its test
POST Cards
Expansion card used to read and display the POST codes
Useful for “dead” systems

9. The Boot Process
Power supply circuitry test for proper voltage then sends signal down “power good” wire to awaken the CPU
CPU sends a built-in memory address across address bus which is the first line of the POST program in the system ROM
Once the POST program is done, it passes control to the last BIOS function, the bootstrap loader
The bootstrap loader reads the CMOS data to find the OS, bootable drives
If a valid boot program is found in a boot sector, it is run; otherwise the next device is tried
The OS is then loaded
Preboot execution environment (PXE) allows for the retrieval of an OS over a network for booting

10. Care and Feeding of BIOS and CMOS
Losing CMOS Settings
How do you know?
CMOS configuration mismatch
CMOS data/time not set
No boot device available
CMOS battery state low
How did it happen?
Pulling and inserting cards
Touching the motherboard
Faulty power supplies
Electrical surges
Dead battery
Flashing ROM

11. UEFI Unified Extensible Firmware Interface Replaces BIOS
UEFI support 32-bit or 64-bit booting
UEFI handles all boot-loading duties
UEFI is not dependent on x86 firmware