How does your computer maintain its configuration?

The BIOS configurations of our computers are always maintained, even when our systems are powered down and unplugged from a power source. How do our computers maintain their configurations, even when unplugged?

A) CMOS memory can maintain configuration information without power

B) The BIOS configuration of the computer is written to the hard drive and read during the power-up process

C) The CMOS is constantly powered with a small battery on the motherboard

D) The BIOS uses a default configuration each time the computer starts

The answer: C) The CMOS is constantly powered with a small battery on the motherboard

CMOS memory needs power, and it’s not uncommon for older computers to start “forgetting” their configuration after they are disconnected from a power source. If your system can’t keep a configuration, use your multimeter to check the voltage of the small battery on the motherboard.

The incorrect answers:

A) CMOS memory can maintain configuration information without power
As mentioned above, CMOS memory does need power to maintain the information.

B) The BIOS configuration of the computer is written to the hard drive and read during the power-up process
A computer may not have a hard drive, so the BIOS can’t count on any storage to be available prior to startup. Of course, there’s the chicken-and-egg problem of the BIOS not having a configuration of the hard drive, so therefore can’t pull a configuration from a device it doesn’t know about.

D) The BIOS uses a default configuration each time the computer starts
A BIOS has many different settings, including hardware configurations and passwords. A single configuration wouldn’t work with most computers!

Want to know more? Watch “BIOS and CMOS Overview.” What really happens when you start your computer? In this video, we’ll show you how the BIOS handles the most basic operations of your personal computer and how the CMOS stores all of your important configuration information. We’ll also show you how to use VMware Player or Microsoft Virtual PC to create a test lab on your computer where you can test BIOS changes without modifying your PC settings.