PC Hardware in a Nutshell, 3rd Edition

Configuring CMOS

Each time a system boots, the BIOS boot screen appears momentarily. While this screen is being displayed, pressing a designated key runs the CMOS Setup program, which resides in firmware. CMOS Setup is used to configure CMOS and chipset settings ranging from those as obvious as the Date and Time to those as obscure as memory timings and bus settings.

Tip

Recent Intel motherboards replace the standard BIOS boot screen with an Intel-logo splash screen. Display the standard BIOS boot screen on such systems by pressing the Esc key while the logo is visible.

To invoke CMOS Setup, you normally press F1 (AMI), the Delete key (Award), or F2 (Phoenix). Other BIOS manufacturers use different keys, and some system and motherboard manufacturers modify a standard BIOS to use another key. The key that invokes CMOS Setup nearly always appears on the BIOS boot screen, but if your BIOS boot screen doesn’t show that key, try the Delete key, F1, F2, F10, Ctrl-Alt-S, or refer to the documentation.

The exact appearance of CMOS Setup and the available options depend on the chipset, the BIOS make and version, and changes made to the BIOS and CMOS Setup programs by manufacturers. For example, two motherboards may use the same chipset, processor, and BIOS, but one may give users complete freedom to configure chipset options, while the other allows users access to only some of the settings and uses hard-wired values for other settings.

All BIOSs default to a reasonable set of CMOS settings, ...