Beginning of the Boot.
The Motherboard and CPU The motherboard is the main circuitboard of a microcomputer. It contains the central processing unit (CPU), the Basic Input/Output
System (BIOS), memory, mass
storage interfaces, serial and
parallel ports, expansion slots, and
all the controllers for standard
peripheral devices like the
keyboard, disk drive and display
screen.
BIOS stands for Basic Input/Output
System. It is the lowest-level
software in the computer; it acts as
an interface between the hardware
(especially the chipset and
processor) and the operating
system. The BIOS provides access
to the system hardware and enables
the creation of the higher-level
operating systems that you use to
run your applications.
The Startup BIOS Controls the
Beginning of the Boot
• Contained on motherboard firmware chip
• Successful boot
– Hardware, BIOS, operating system all perform without
errors (beeps, text or voice messages)
• Boot functions
– Startup BIOS runs POST and assigns system resources
– Startup BIOS program searches for and loads an OS
– OS configures system and completes its own loading
– Application software is loaded and executed
Step 1: Post and Assignment of
System Resources
• Turn on PC power
– Processor begins the boot by initializing itself
– Turns to startup BIOS for instructions
• Startup BIOS first performs POST
• 17 key steps involved
Step 2: Startup Bios Finds and
Loads the OS
• Startup BIOS looks to CMOS RAM to find boot
device
Step 2: Startup Bios Finds and
Loads the OS (cont’d.)
• Tracks: concentric circles on drive
• Sectors (segments): portion of a track
– Holds up to 512 bytes of data
• Master Boot Record (MBR)
– Contains master boot program and partition table
• OS boot record
– 512-byte sector
– Second sector on drive behind MBR
– Contains small program pointing to a larger OS
program file (BootMgr or Ntldr)