How to enter the system BIOS/CMOS
Note: Many people will interchange the terms “bios” and “cmos“. For the purposes of this article, the term “bios” will be used.
BIOS = Basic Input Output System
Brief Overview
The BIOS is a program pre-installed on computers (with the exception of Macs) that the computer uses to start up. The CPU accesses the BIOS before the operating system is loaded. The BIOS then checks all your hardware connections and locates all of your devices. If everything is OK, the BIOS loads the operating system into the computer’s memory and finishes the boot-up process.
Since the BIOS manages the hard drives, it can’t reside on one, and since it has to be available before the computer boots up, it can’t live in the RAM. The bios is located in the ROM (Read-Only Memory) of the computer. It resides in an eraseable programmable read-only memory (EPROM) chip on the computers motherboard. So, as soon as you turn your computer on, the CPU accesses the EPROM and gives control to the BIOS. The BIOS is also used after the computer has booted up. It acts as an intermediary between the CPU and the I/O (input/output) devices. Because of the BIOS, your programs and your operating system don’t have to know exact details (like hardware addresses) about the I/O devices attached to your PC. When device details change, only the BIOS needs to be updated. You can make these changes by entering the BIOS when your system starts up. To access the BIOS, hold down the appropriate key as soon as your computer begins to start up.
On the majority of todays computer systems, the bios is entered by pressing a key or a key sequence on power up. Usually on the first screen display you see will be the instructions for the key sequence required to enter the bios/cmos. The BIOS setup program can normally be entered only during the boot process, either on a cold boot, or a warm boot (after hitting {Ctrl-Alt-Del}). Some setup programs (example; early ACER systems) will let you go into the setup program using a key combination once the system has fully booted/started.
The use of the delete key {Del} to enter the setup program during boot is becoming standard. AMI and Award BIOS, and some others as well now use this. Older BIOSes can use any of strange key combinations, including Esc, F1, F2, F10, Ctrl-Esc, Alt-Esc, Ctrl-Alt-Esc, Ctrl-Alt-Enter, Ins or others. If one of the above key sequences does not enter the bios setup program, you will have to seek out a manual for your system, or go the the manufacturers website for instructions. Phoenix (Hewlett Packard) use F1. The POST (Power On Self Test) screen (or “Diagnostic” screen) will be hidden by default on some systems, such as HP, Dell, and Compaq. Instead you will see a screen bearing the logo of the manufacturer. When this screen first appears, this is when you enter the key sequence for the bios setup. This manufacturers “splash” screen can be set to hidden (allowing you to see the boot process) once you enter the bios.
Once you enter the bios setup, you will (usually) end up in the first basic setup screen for your system. This is where the time and date, floppy drive and hard disk parameters are set. There may be another screen or section for hard disk or IDE auto detection. If utilized, this will set the hard disk parameters in this first Basic setup screen.
The boot sequence for system start up will usually be in the ADVANCED (or BOOT with Phoenix bios) section. This is where you can choose the boot device order. For the average user, the sequence is A: (or floppy drive), CDROM drive, then the first IDE hard disk (labeled 0 or 1, depending on how your system is designed). On todays systems, there is also a choice for booting to “other devices”, such as a Network. (When the bios is reset to factory defaults, this boot sequence is usually used.) On some older systems, the CDROM may show up as NONE. This is normal for these systems. The CDROM is usually identified on the POST screen, such as; “Found - LG CRD-8320B” or similar. So even though it’s not listed in the bios, the system knows it’s there.
One last thing to mention, some bios will not recognize changes, new RAM (and other devices) unless you set the “Reset Configuration Data” option (if it exists in your bios) to YES. Once you save your changes, and the system boots successfully with the new changes, this switch will be automatically reset to NO, until you enter the bios once again and change it.
