A+ Hardware Service Technician: System Architecture

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BIOS

What is the BIOS?

The BIOS (Basic Input Output System) is the chip that contains low level software for configuring the system's capabilities and communicating with the hardware. The BIOS previously was stored in the ROM, though most present day computers have the BIOS stored in EEPROM, an electronically erasable programmable ROM. The BIOS communicates between the software and the hardware so fewer conflicts present themselves.

BIOS Operation

When you first enter setup on a computer, you see many options for configuring your computer. Typical options include the automatic detection of IDE drives, option to enable/disable the processor cache, Plug’N’Play feature detection, password protection, time/date settings, IRQ settings, and more.

Typically, the BIOS stores its configurations in the CMOS (Complementary Metal-Oxide Semiconductor). The CMOS is powered by a small battery so it can retain its settings after the power is turned off. The CMOS is usually not upgradeable, but the battery used to power it is usually easily upgradeable.

Troubleshooting and the BIOS

Since the BIOS contains the low level software controlling the computer, you may need to replace it in earlier PCs if you have to upgrade the hard drive.

If you continually lose your settings in between power cycles of your machine, your CMOS battery may need to be replaced. This can be found on the motherboard and is typically a standard battery you can get replaced at most computer shops or electronics stores.

Example Screenshots of Different BIOSs (Click to open larger in a new window)

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