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Last modified: Monday, August 23, 2004 

(bī´ōs) Acronym for basic input/output system, the built-in software that determines what a computer can do without accessing programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.

The BIOS is typically placed in a ROM chip that comes with the computer (it is often called a ROM BIOS). This ensures that the BIOS will always be available and will not be damaged by disk failures. It also makes it possible for a computer to boot itself. Because RAM is faster than ROM, though, many computer manufacturers design systems so that the BIOS is copied from ROM to RAM each time the computer is booted. This is known as shadowing.

Many modern PCs have a flash BIOS, which means that the BIOS has been recorded on a flash memory chip, which can be updated if necessary.

The PC BIOS is fairly standardized, so all PCs are similar at this level (although there are different BIOS versions). Additional DOS functions are usually added through software modules. This means you can upgrade to a newer version of DOS without changing the BIOS.

PC BIOSes that can handle Plug-and-Play (PnP) devices are known as PnP BIOSes, or PnP-aware BIOSes. These BIOSes are always implemented with flash memory rather than ROM.

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For pages about BIOS . Also check out the following links!

Related Links

BIOS information page 
Provides an excellent source of information on BIOS, including links to general information, upgrades, AMI, AWARD, MR BIOS and Phoenix BIOS.

BIOS Settings 
A comprehensive view of the most common settings that are used in modern PCs, with full explanations as to what they are and how to set them. This page is from "The PC Guide".

BIOS Settings - Advanced Chipset Features 
Extensive information on the settings associated with fine-tuning control over the system cache, memory, and I/O buses, to optimize performance. This page is from "The PC Guide".

PC Tweaking Basics: The System BIOS 
Here's an introductory guide to the system configuration station that can make the difference between a smooth-running and screwed-up PC (or between a timid novice and fearless power user) -- the BIOS.

System BIOS 
Explains what BIOS is and contains details on its function and operation, components and features, setup programs, and settings. This page is from "The PC Guide".

The Definitive BIOS Optimization Guide 
There's only one way to decide what's the best settings for your own BIOS. Read the BIOS Optimization Guide and learn how to optimize your BIOS.

Wim's BIOS page 
A collection of links to information on FlashBIOS, BIOS settings, Award/AMI BIOS number references, FAQs, and links to related BIOS Web sites.

BIOS Components and Features
Describes several components and features that are commonly found as part of a modern BIOS. This page is from "The PC Guide".

BIOS information and related topics
Information on PC ROM BIOS and related topics, including Power-On-Self-Test (POST), internal diagnostics, system BIOS, BIOS setup utility, hardware, literature, addresses, and example code.

BIOS information page
This sites hosts a collection of information on BIOS. There are links to the BIOS Survival Guide, information on BIOS memory timing, flash BIOS updates, and related Web sites.

BIOS setup information
This how-to document details a number of methods for accessing your PC at the chipset level, thereby gaining access to a number of BIOS advanced chipset options that are not available in the BIOS setup.

BIOS System Boot Operations
Describes what is involved in booting a PC, including a discussion of the steps in the system boot process, and a look at the power-on self-test (POST) that is conducted whenever the system starts up. This page is from "The PC Guide."

Compguys Techweb
Offers in-depth articles on Fdisk and PC BIOS, with information resource on Fdisk and hard disk partitioning.

Hard Disk BIOS and Capacity Factors
Describes issues related to how the BIOS and operating system interact with the hard disk, and BIOS-related issues and problems. Includes a full look at the many capacity limitations inherent in using IDE/ATA interface drives, and other BIOS restrictions on hard disk capacity. This page is from "The PC Guide."

Maximum Hardware - Computer Hardware Performance Site
Offers a collection of up-to-date information relevant to computer hardware performance. The site includes product information and news, a BIOS upgrade guide, performance reports, links to related sites, information about 3D games, and articles on video accelerators, motherboards, and overclocking.

Microsoft Bus and BIOS Design for PC Hardware
Contains links to technical information about BIOS and bus class design issues.

PC motherboard and system device reference
Comprehensive motherboard reference, covering all the major motherboard components. Looks at the physical motherboard, chipset, system buses, system cache, system resources, and the system BIOS.

PC system BIOS reference
Reference information on the system BIOS. Includes a complete look at what the BIOS is and how it works. Covers components and features, the boot process and the setup program. Includes a detailed reference covering dozens of individual BIOS settings.

System BIOS Functions and Operation
Clear and detailed description of how the system BIOS works interacts with the operating system and hardware. This page is part of "The PC Guide".

Troubleshooting BIOS beep codes
Describes how to interpret POST (power-on self test) beeps. Covers AMI, Award, and Phoenix BIOSes. From "The PC Guide".

Troubleshooting the Motherboard and System Devices
Focuses on problems related to the motherboard and system devices, including the components of the motherboard, along with system devices such as the cache and I/O buses, the BIOS and CMOS memory, system resources, and features such as Plug and Play. This page is from "The PC Guide."

What is BIOS? Mini-FAQ
Provides introductory information on BIOS and instructions on changing configurations using CMOS and accessing CMOS setup.

Yahoo!'s BIOS page
Yahoo!'s directory of BIOS.

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