The BIOS controls the very basic functions of a computer and is responsible for such things as checking that the processor and memory are present and working, and looking for a disk drive to boot from.
The BIOS also handles the basic configuration of other components too, such as sound, graphics cards and various ports. The operating system may take care of making these components actually work but without the BIOS, it wouldn't get very far.
Under normal circumstances, the BIOS goes about its business without drawing any attention to itself, apart from perhaps displaying the odd message on your monitor when you first turn your PC on.
There are times, however, when you will need to delve into its recesses, such as when you fit a new hard disk or processor, or even upgrade your operating system.
Most PCs come with a manual that claims to explain the BIOS but these usually gloss over even the most basic of details. What you really need is a plain English guide that tells you everything you need to know. Just like this one, in fact!
BIOS basics
The BIOS is stored on a chip on the PC's motherboard. There are countless different makes of motherboard but only two companies actually produce BIOS chips - Award and AMI.
Each manufacturer's BIOSs look a bit different, as do BIOSs on different PCs, but the BIOS screen layouts and options are fairly standard and once you're familiar with one, you should be able to figure out another.
So, first things first: how do you get to the BIOS? Most computers will show the key on the keyboard you need to press when the computer is first turned on. It is usually F1, F10, F11, F12 or the Delete (Del) key - look for an on-screen message along the lines of "Press F1 to enter Setup".
Some computers will only let you enter the BIOS when the PC is first turned on and not after a reset. Sometimes you just have to guess and try tapping the different keys when the computer starts to find out.
The first thing to remember when entering the BIOS is not to change any setting that you don't understand. Some options can stop your computer from working properly, or at all, and some can even stop you from getting into the BIOS again to change them back.
If you decide to change several options, it's a good idea to change one at a time and restart your computer after each one. That way, if one of the changes causes problems, you'll know what it was and can easily change it back.
Getting around
Almost all BIOSs are organised into a series of 'screens', with each being accessed from a menu running across the top. Enter one screen and there may be further options that take you into sub-screens. Pressing the Escape (Esc) key will return you to the previous one.
The first screen you'll probably see when entering the BIOS will show the date, time, a few other useful bits of information and instructions for navigating between the screens and making changes.
For example, on our computer, options you can change are yellow and surrounded by square brackets. Text that is coloured grey is information and cannot be selected. You can change settings by pressing the + and - keys or you can press the Enter key to display a list of options.
The other two important options in the main screen are 'Exit Without Saving' and 'Save & Exit Setup'. They are self-explanatory but it is worth emphasising that if you have changed something and are in any doubt about whether it will damage your computer, select Exit Without Saving and then try again.
Why change BIOS settings?
Fitting new hardware can sometimes mean you have to edit the BIOS. Most computers will find any new hardware automatically but sometimes you need to tell the computer where it is.
The most common task is fitting a new hard disk. The BIOS can detect new drives automatically but as this increases the boot time, this feature is often disabled by default. In this case, the new drive won't be detected when the computer starts.
To change this, enter the BIOS in the usual way and select the Standard CMOS Features option. Here you will see a list of the drives connected to your computer as IDE Primary Master and Slave, and IDE Secondary Master and Slave.
Move the cursor down to where it says (None) and press return. Select the Auto option and your hard drive should be detected automatically.
Get your boots in order
A very useful setting the BIOS allows you to change is how your computer boots. When it first starts, the BIOS looks for a disk containing an operating system to boot from.
Usually, this is the hard disk but there may be times when you want to boot from a floppy disk or a CD-Rom. Which drives are checked and in what order is determined by the Boot Order in the BIOS.
Changing the Boot Order can make your computer more secure as it gives you more control over how it starts. Even if Windows is password-protected, it is possible for someone to start the computer with a floppy disk or a CD.
Alternatively, if you want to stop someone messing around with your computer, you can do so by restricting how the computer starts and make your computer look on your hard drive for an operating system first.
Enter your BIOS in the usual way and enter the Advanced BIOS Features screen. You will either see a list of the devices the BIOS checks, or an option to change the boot order.
To make our computer more secure we are going to change the first boot device to HDD-0, which is short for Hard Disk Drive 0, or the first hard disk, in other words. Move down to First Boot Device and press Enter to see a list of devices the computer can boot from. Move down to HDD-0 and press Enter again.
Changing the boot order for troubleshooting is effectively the reverse of this process. There are lots of very good troubleshooting tools that you can load from CD or floppy disk. If there are problems with the hard drive, you may need to make the computer look elsewhere first.
This might be necessary if Windows has a fault that stops it from loading properly or if you want to boot from the Windows CD-Rom in order to reinstall it. Return to the Advanced BIOS Features screen and change the First Boot Device to the media that you want to boot from.
Keeping your PC secure
Setting a password on your BIOS is an excellent way to make your computer more secure. A password in Windows only restricts access to Windows and can be bypassed with a little knowledge; a BIOS password protects the computer from the moment it is switched on.
There are two kinds of password that you can set in the BIOS. The first and most important password gives permission to change options in the BIOS itself and is commonly called a Setup password. This is particularly useful if you have stopped the computer from booting from CDs or floppy disks and don't want anybody to change this.
The other password must be entered as soon as the computer is switched on, even before the option to enter the BIOS appears - a User password. This is the first line of defence you can add to your computer and is very effective.
A word of warning about getting too overconfident about these passwords, however. It is possible to reset the BIOS if you can access the inside of the computer and it does not stop someone from removing the hard disk to read on another system.
If the files on your computer are really secret, consider buying a case that can be locked to stop people from changing these options.
POST haste
One of the most important jobs of the BIOS is the POST, short for Power On Self-Test. This makes sure that all of the important bits of the computer are working properly. An option you might want to change is how thorough these tests are.
Modern hardware is much more reliable than it used to be so some of these checks are much shorter. For example, older computers used to check that every bit of memory was working before they started.
Now the computer just looks to make sure that all the memory is there. Skipping these tests saves time but can stop you from finding out what is wrong if your computer starts playing up. Many BIOSs have options to disable quick starting and this should be something to try if the computer keeps crashing.
Most BIOSs also come with saved settings for different situations. The default settings are useful if you ever want to return your computer to the settings it had when you first bought it. Optimum settings should give you the best performance possible from your computer but the most useful collection of settings is the Fail Safe setting.
This turns off all of the high-performance options and gives your computer the best possible chance of starting. If you have changed an option in the BIOS that is preventing Windows from working, this is the best way of solving the problem.
The disadvantage of this option is that you may find you computer slower than it was before.
Sound advice
Adding a new soundcard to your computer can sometimes require editing the BIOS. Most new motherboards have a soundcard built in. If you want to add a new one, you will need to disable the on-board soundcard first.
To do this, go into the Integrated Peripherals screen from the main BIOS menu. The options in this menu control the hardware on the motherboard such as the USB, serial and parallel ports.
Move down through the options until you reach the option AC97 Audio. If it says Auto or Enabled this means the computer will try and use the soundcard built into the motherboard. Press Enter and select Disabled from the menu. You can now safely install your new soundcard.
The ins and out of it
We hope this has made a rather tricky part of your computer more accessible. Unfortunately, it is not possible to cover everything here, as many parts of the BIOS are specific to individual computers. In this instance, it is worth checking the manual that came with your computer or searching for your motherboard on the web.
You should find the name of the motherboard on the first screen you see when your computer checks for memory and disk drives. Alternatively, it is usually written in white on the motherboard.
Tweaking the settings in your BIOS should help you to get the most from your computer but it is one area that demands a lot of caution.
BIOS optimisation
If you are willing to do the research into your hardware, it is possible to improve your computer's performance simply by adjusting the BIOS.
Good-quality memory can be set to run at faster speeds than normal and so can give a real speed boost. The setting relates to the latency of the memory. Look for the full specifications of your memory to see how fast it can run.
There are sometimes options to reduce the amount of time needed to start your computer. Enable the fast POST option to only perform a quick hardware check. Disabling the Floppy Seek at Boot-Up option will also increase the start-up speed.
You can also 'overclock' your computer from the BIOS. This allows you to run your computer faster than it was designed for. Despite the performance benefits of overclocking, it immediately invalidates your warranty and can permanently damage your computer. Make sure you do your homework first.
Flashing the BIOS
Motherboard manufacturers regularly update the BIOS for their products, both to fix problems and add new features. The updates are available for download from the manufacturers' websites and are installed with a process called 'flashing', because the BIOS is stored in flash memory.
Flashing the BIOS is a straightforward process but it can usually only be done by booting the PC from a floppy disk - one reason why the floppy drive isn't quite extinct yet.
It's not a foolproof process, however, since an error during the flashing can render the BIOS - and hence the PC - unusable. Such errors are few and far between and generally only occur if, for example, a power cut interrupts the process.
Unless you're experiencing problems with your PC that can be traced back to the BIOS, the best advice is to leave it alone. Many manufacturers take a dim view of people who flash their BIOS without consulting them first and they may quibble over any resulting warranty repairs.
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