CYBER NOTES March, 2005 by Dave Benore

Understanding the BIOS in a computer

This month’s column is directed to those who wish to learn more about how their computer works. It’s about your computer’s BIOS (Basic Input Output System).

Last September I wrote about the boot-up process a computer goes through as it starts up from scratch. Let me repeat a paragraph from that column:

“When the electrical power is first turned on, the computer, in that instant, is totally dumb—without instructions of any kind. The act of power flowing into the computer causes it to “boot-up”. There is some physical wiring inside the computer that gives the computer its first instructions. Those instructions tell the computer where to look for more detailed instructions. Normally, the computer first looks at the floppy drive if it has one, then, if there is no floppy disk in the drive, it looks at the hard disk. (This sequence can be changed. The computer can also be directed to look at the CD drive.)”

That paragraph over-simplified one part—the part that said: “There is some physical wiring inside the computer that gives the computer its first instructions. Those instructions tell the computer where to look for more detailed instructions. Normally, the computer first looks at the floppy drive if it has one,…” This statement is true but not complete. Actually, the physical wiring referred to tells the computer to read the BIOS first and then look for the operating system starting with the floppy drive.

The BIOS is the name applied to a very special section of separate memory—separate from RAM or the hard disk. This special memory holds set-up instructions for the computer to use at start-up. It is powered by a very small battery buried inside the computer. More about this battery later.

The BIOS tells the computer all it needs to know about things like the size and type of your hard disk and RAM, among other things. Without this information the computer does not know enough to accurately communicate with these devices. The BIOS also contains the sequence that the computer goes through in looking for the operating system (Windows). The normal sequence is to look first at the floppy drive, if the computer has one, then the hard drive, then a CD drive. As soon as the computer finds the operating system files it stops looking further and uses the instructions.

So why does a person care about the BIOS? One reason is you can change it! When a computer is first turned on, in the first few seconds, it displays the function key to push to “enter” the BIOS. Frequently the key is F2, and the display probably says something like “F2-Setup”. It must be pressed while the monitor is displaying the key number however. Once the screen starts showing the Windows logo it’s too late. One has to reboot the computer to try again.

Once in the BIOS, you can take all day to poke around and learn what is there and how to change it. However, do not change stuff until you understand what the change will do. This is one area that can be changed so your computer will not run! But you can look at everything without changing it. Just the looking leads to more knowledge.

The good news is that any change can be undone, or changed back, if you have recorded the original settings. (Write down any changes you make from the original settings.) "Settings" is the operative word here. The BIOS controls the basic setup of your computer’s communications. The operating system controls the rest.

If another change is required, you have to turn off the computer and reboot to gain access to the BIOS again. The BIOS is programmable. When you enter the BIOS and make a change, and save that change, you are actually reprogramming the BIOS. (The earliest PCs had hardwired BIOSs and could not be reprogrammed.) When in the BIOS the screen will show which keys do what (the mouse does not work here because the operating system has not yet loaded).

Back to the question, “So why does a person care about the BIOS?” Well, since the BIOS is powered by a battery, and batteries have a finite life, what happens when the battery runs down—and how long does that take?

The battery should last at least 4 years, and 5 to 8 is possible. The signs that a battery needs replacing can be that the computer clock no longer keeps the correct time. That used to be an early sign. The next sign is that the computer won’t run correctly. It may give strange error notices like “can’t find the hard drive”.

The good news is that the battery does not cost much. That bad news is the computer must be opened up to gain access to the battery. It is easily replaced in most computers. But, the BIOS will probably need to be reprogrammed. (This is where a copy of the original settings comes in handy.) Do not open up the computer yourself unless you know what you are doing. Static electricity from your body can ruin the internal electronics.

So, regarding the boot-up process, as Paul Harvey would say, “that is the rest of the story”. Happy Computing.