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What Is the BIOS?

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This chapter is from the book

What Does It Do?

Here is a breakdown of what the motherboard BIOS actually consists of:

  • Power-on diagnostic tests

  • System configuration utility

  • Bootstrap loader

  • BIOS interface

When you boot up the computer, it initiates the POST (Power-On Diagnostic Test). The POST serves as a quick-and-dirty way to make sure that all the critical components are functioning.

After the POST sequence completes, you are given the opportunity to access the system configuration utility. This utility allows you to configure and modify a range of features. These BIOS features show you just how important the BIOS is.

These BIOS features control every aspect of the computer, from the speed at which the processor runs to the transfer mode of the hard disk. It goes without saying that these BIOS features are the reason why I'm writing this book. We go into details later in Chapter 4.

After the short delay, the BIOS starts the bootstrap loader routine, which scans for a valid master boot sector on all available drives. This can be anything from a hard disk to a CD-ROM drive. The master boot sector is just a predetermined area containing code that initiates the loading of the operating system.

When executed, the master boot sector turns over the booting process to the operating system by loading the operating system's boot sector. The operating system then starts loading up its core files.

In most cases, this is where the BIOS' role ends because current operating systems employ their own 32-bit or 64-bit drivers, which offer far superior functionality and performance to the BIOS' basic drivers. However, the BIOS' core drivers still have some importance.

Even modern operating systems like Microsoft Windows still need to use the BIOS' basic drivers, albeit only in their troubleshooting or "safe" modes. This is because the core BIOS drivers have been standardized a long time ago, and every piece of hardware made since then is backward-compatible with them.

While these core BIOS drivers may be slow and primitive, they are guaranteed to work with any hardware designed for the PC. That's why they are still an integral part of every PC.

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