Transcript BIOS Introduction

Introduction to the BIOS
BIOS – Part 1
© Richard Goldman
Rev. January 4, 2001
System BIOS
• BIOS = Basic Input/Output System
• Interface between the hardware and the
Operating System of a computer
• System BIOS is installed on the motherboard
and is system dependent.
• Contained in a Read Only Memory (ROM) chip.
• Note: Other hardware devices (adapter cards)
can also have their own BIOS.
RTC/NVRAM
Real-Time Clock/Non-Volatile RAM
• Keeps the system time and date.
• Stores the system configuration data.
• Stores the Plug and Play settings shared by the
BIOS and the OS.
(ESCD – Extended System Configuration Data)
• Uses CMOS technology.
(Complementary Metal-Oxide Semiconductor)
• CMOS memory is maintained and the system
clock is powered by a lithium battery.
System BIOS
System BIOS
1. POST Program
(Test and Configure)
2. Startup Routine
(Bootstrap Loader)
CMOS RAM
(RTC/NVRAM)
1. Time and Date
2. System Configuration
3. ESCD (PnP settings)
(Extended System Configuration Data)
3. Setup Program
(System Configuration)
4. System BIOS
(Hardware Drivers)
Lithium Battery
The BIOS firmware contains:
• A setup program used to set and store system
configuration information in the CMOS RAM.
• A Power On Self Test (POST) that tests the
major components of the computer when it is
first turned on.
• The startup program (the bootstrap loader) is
used to locate and start the loading of the
operating system.
• A collection of drivers that allows the operating
system to communicate with the hardware.
System Layers
Applications
API Application Program Interface
Windows
DOS
BIOS
Hardware
Drivers
The BIOS Software
• Comes from:
– Motherboard ROM BIOS
– Adapter card ROM BIOS
– Loaded form disk (hardware drivers)
• Software that is needed at startup needs to be
located in a BIOS.
• The System BIOS will scan for and run other
BIOS during startup.
• Common devices with their own BIOS:
– Video, SCSI, NIC’s, Hard Drives, etc.
Types of ROM
(Non-volatile RAM)
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ROM
PROM
EPROM
EEPROM
Read Only Memory
Programmable ROM
Erasable PROM (UV erasable)
Electronically-Erasable PROM
(Flash)
BIOS Manufacturers
• AMI – American Megatrends Inc.
• Award Software (now owned by Phoenix)
• Phoenix Software
BIOS Identification String
• Displayed in lower left corner of screen during
startup.
• Unplug keyboard before turning on power to
cause error and lock display so that you can
view ID string.
• Obtain updated BIOS directly from Computer
OEM (if available).
• Unicore and on-line sources such as
hardwarehell.com are good sources for BIOS
information and upgrades.