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Your PC's Bios Explained

Introduction to your computer's BIOS:

A single beep from your PC's speaker at startup is a wonderful sound to hear. Just ask anyone who has ever turned on her computer and suffered the agony of hearing several beeps and then nothing. 

When you purchase a new PC, it will arrive with the BIOS (Basic Input/Output System), already installed on an EPROM (Erasable Programmable Read-Only Memory) chip that resides on the computer's system board.

When you start your computer, the CPU (Central Processing Unit), sends control of the PC to the BIOS routine. The BIOS is part of the POST (Power-On Self Test) of the computer (the test that verifies your PC's hardware prior to booting).

After the CPU gives the BIOS the "go ahead", it begins looking for all the components and peripheral devices attached to your  computer. The CMOS memory chip (complementary metal oxide semiconductor) stores the data that is used by the BIOS setup and testing routines. In a nutshell, the CMOS  chip enables your PC to retain the startup and BIOS information even when the power is removed from the computer. The CMOS chip is located on the system board in an always-on state. A small battery on the system board powers the chip when the computer's power is turned off. 

When we wake up in the morning, our brain remembers that we have eyes, ears, a nose, etc. We remember the town that we live in. We know how to get to work, to the grocery store, and back home without having use a map for directions each time.

Your PC works much the same way. Without some type of memory device to "remind" the computer about what's where, the operating system and other software wouldn't be able to locate each part of the computer and its components every time they are executed. Fortunately, the BIOS memory chip takes care of that for the CPU, operating system, and computer components. 

How the BIOS works:

Every PC comes with the BIOS pre-installed on the system board. System board manufacturers work hand-in-hand with BIOS manufacturers to ensure that the information stored in the BIOS is specific to the needs and components of each model of system board.

Although there are quite a few BIOS manufacturers, the two market leaders are American Megatrends (AMI) and VIA.

Simply put, the BIOS is a computer program, not an actual device. It informs the computer during startup about all the devices (input and output) that are attached to the PC. The BIOS also informs you if there is a problem with your PC. It does this by looking for known devices and making sure they are still attached to the computer.

If the BIOS detect a problem during the POST, it sends a series of beeps to the computer's speaker. These beeps inform the user of what the problem is as best it can. For instance, if your video card has stopped working, the BIOS senses that it has died or is not installed. The BIOS then sends a series of beeps to the PC speaker to let you know about the problem. Pretty neat, huh?

But there is a problem: No two BIOS manufacturers use the same beep series. This is why it is important for you to know which BIOS software is used in your specific computer. We'll explain how to find this out later.

How do you know if the BIOS is working? If your computer starts up and you hear a single short beep, the BIOS is working and everything is ok.

But if you turn on your PC and nothing happens at all, the problem is most likely in your power supply (assuming that you have it plugged in to an electrical outlet). The BIOS is probably working just fine, but the computer can't start due to a lack of power.

If everything is working correctly, the BIOS will find all of the attached input/output devices, sound a single short beep through the speaker, and the computer will boot up as usual. 

OK, so who's the boss? Is it the BIOS, CMOS or POST? Well, if we had to choose, it would probably be the POST (Power On Self Test). The POST is the process the BIOS uses to retrieve the information from CMOS memory to test and start up the PC (by tf support allender). Remember, the BIOS setup information is stored in the CMOS memory chip which is maintained by an onboard battery. 

Three ways to change or update the BIOS:

  • Unlike ROM (read-only memory), the EPROM BIOS information can be changed. The term used to describe changing the BIOS software is "flashing". You may have heard someone say that they need to "flash the BIOS" with a new update.

    Computer components change on a regular basis. Your PC's BIOS needs to be flexible enough to be able to change to support new hardware. All modern PC's allow the user to update the BIOS software when necessary.

    The standard is to offer the user an easy way to access the software via a hotkey during the startup process. This hotkey is usually the Del key, the F2 key, or a combination of keys.

    Start your computer and look for a message on the screen letting you know which key(s) to press to enter the BIOS setup routine. The BIOS setup (also called the CMOS setup) allows the user to make changes to the information stored and save them.

    For instance, you have just added an external modem to your computer on serial port number 1 (Comm1). No matter how many times you install the new modem drivers, you can't get Windows to recognize it. Chances are that the BIOS doesn't know about the new modem. Entering the BIOS setup and enabling the use of Comm1 will fix the problem and let the PC know that a modem is attached to that port. This is the most common use of the BIOS setup routine.
    Warning: It's very easy to totally mess up your system by making BIOS setup changes! So be very careful and make sure you know what to change and how to do it.

    Always make changes by following the manufacturer's instructions when possible. Changing the wrong BIOS settings can render your PC unable to operate and completely useless. 

  • The second method of updating the BIOS is by using a "Flash BIOS Update" available from the manufacturer of the BIOS. This is simply a software program that the BIOS manufacturer sends out periodically to make sure that your BIOS conforms to new equipment and standards. You can usually get this software upgrade from the BIOS manufacturer or the system board manufacturer.

    Be very careful when you install the software. Be certain that the upgrade is for your specific BIOS. Always follow the manufacturer's instructions to the letter!

  • The third way to update the BIOS is by simply replacing the BIOS chip itself. Replacing the BIOS chip altogether may be your only recourse if you have an older system board. This procedure is best left to a qualified PC Technician.

How do I know which BIOS I have?

This one is easy: Your computer will tell you! If you're a fast reader, you'll see the BIOS name and version on the screen the moment you turn the computer on.

If the information scrolls away before you have a chance to read it, you can enter the BIOS setup and retrieve the information from there. You can also contact the system board manufacturer and ask them which BIOS was installed on yours (you'll need the model number). 

As stated earlier, the beeps that you hear during start-up mean something. They can provide useful information on any problems that the BIOS encounters during the POST.

Contact your BIOS manufacturer to discover what each beep series means. This information will help you find out why your computer has stopped working and aid with fixing the problem.

Michael List is a Network Systems Administrator and Web Master.

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