What exactly does the BIOS do and why do you need to become familiar with it? When you host with ServerBeach, this is something that you’ll never need to deal with or worry about. But if you have to configure the BIOS on a computer that you’ve purchased for home or personal use and you find yourself lost or a little confused on what exactly you need to do, we hope this information will provide a little insight. Let’s start by describing the role of the BIOS.
The BIOS software has a number of different roles. The most important role is to load the Operating System. When you turn on your computer, the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the Operating System because the Operating System is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:
- A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly.
- Activating other BIOS chips on different cards installed in the computer – For example, SCSI and graphics cards often have their own BIOS chips.
- Providing a set of low-level routines that the operating system uses to interface to different hardware devices – It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting.
- Managing a collection of settings for the hard disks, clock, etc.
The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM.
So now that you’re familiar with the role of the BIOS, let’s look at some of the steps the BIOS goes through to get your computer ready to run.
Whenever you turn on your computer, the first thing you see is the BIOS software doing its thing. On many machines, the BIOS displays text describing things like the amount of memory installed in your computer, the type of hard disk and so on. It turns out that, during this boot sequence, the BIOS is doing a remarkable amount of work to get your computer ready to run. This section briefly describes some of those activities for a typical PC.
After checking the CMOS Setup and loading the interrupt handlers, the BIOS determines whether the video card is operational. Most video cards have a miniature BIOS of their own that initializes the memory and graphics processor on the card. If they do not, there is usually video driver information on another ROM on the motherboard that the BIOS can load.
Next, the BIOS checks to see if this is a cold boot or a reboot. It does this by checking the value at memory address 0000:0472. A value of 1234h indicates a reboot, and the BIOS skips the rest of POST. Anything else is considered a cold boot.
If it is a cold boot, the BIOS verifies RAM by performing a read/write test of each memory address. It checks the PS/2 ports or USB ports for a keyboard and a mouse. It looks for a peripheral component interconnect PCI bus and, if it finds one, checks all the PCI cards. If the BIOS finds any errors during the POST, it will notify you by a series of beeps or a text message displayed on the screen. An error at this point is almost always a hardware problem.
The BIOS then displays some details about your system. This typically includes information about:
- The processor
- The floppy drive and hard drive
- BIOS revision and date
Any special drivers, such as the ones for small computer system interface adapters, are loaded from the adapter, and the BIOS displays the information. The BIOS then looks at the sequence of storage devices identified as boot devices in the CMOS Setup. “Boot” is short for “bootstrap,” as in the old phrase, “Lift yourself up by your bootstraps.” Boot refers to the process of launching the operating system. The BIOS will try to initiate the boot sequence from the first device. If the BIOS does not find a device, it will try the next device in the list. If it does not find the proper files on a device, the start-up process will halt. If you have ever left a disk when you restarted your computer, you have probably seen the message “Non system disk or disk error. Replace and strike any key when ready.” The BIOS has tried to boot the computer off of the disk left in the drive. Since it did not find the correct system files, it could not continue. Of course, this is an easy fix. Simply pop out the disk and press a key to continue.
In the previous list, you saw that the BIOS checks the CMOS Setup for custom settings. Here’s what you do to change those settings.
To enter the CMOS Setup, you must press a certain key or combination of keys during the initial startup sequence. Most systems use “Esc,” “Del,” “F1,” “F2,” “Ctrl-Esc” or “Ctrl-Alt-Esc” to enter setup. There is usually a line of text at the bottom of the display that tells you “Press ___ to Enter Setup.”
Once you have entered setup, you will see a set of text screens with a number of options. Some of these are standard, while others vary according to the BIOS manufacturer. Common options include:
* System Time/Date – Set the system time and date
* Boot Sequence – The order that BIOS will try to load the operating system
* Plug and Play – A standard for auto-detecting connected devices; should be set to “Yes” if your computer and operating system both support it
* Mouse/Keyboard – “Enable Num Lock,” “Enable the Keyboard,” “Auto-Detect Mouse”…
* Drive Configuration – Configure hard drives, CD-ROM and floppy drives
* Memory – Direct the BIOS to shadow to a specific memory address
* Security – Set a password for accessing the computer
* Power Management – Select whether to use power management, as well as set the amount of time for standby and suspend
* Exit – Save your changes, discard your changes or restore default settings
Be very careful when making changes to setup. Incorrect settings may keep your computer from booting. When you are finished with your changes, you should choose “Save Changes” and exit. The BIOS will then restart your computer so that the new settings take effect.
The BIOS uses CMOS technology to save any changes made to the computer’s settings. With this technology, a small lithium or Ni-Cad battery can supply enough power to keep the data for years. In fact, some of the newer chips have a 10-year, tiny lithium battery built right into the CMOS chip.
We’d like to thank HowStuffWorks for the above information. If you’d like to learn how to update your BIOS or learn more about “How Stuff Works“, we encourage you to head on over to their website full of informative articles and screen shots to help get you in-the-know on just about anything and everything.
Filed under: Computers | Tagged: BIOS, Bootup, CMOS, Computers, HowTo, PCI, Periphials, Reboot, software, Technology | 2 Comments »