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PC Tweaking Basics: The System BIOS January 15, 2003 The Core of Configuration In the movies, when the heroine wakes up with amnesia, she puts a hand to her brow and breathes, "Where am I?" When you push your PC's power switch each morning, the machine not only has amnesia but needs to ask, "What am I?" -- for that first millisecond, it doesn't even know it's a PC, let alone that it has X amount of memory, such-and-such type and size of hard disk, and should stay alert for your keyboard and mouse input. The tool that kick-starts your computer, "teaching" it its configuration, how to access memory, and so on, is the BIOS (basic input/output system) -- one of the most essential, powerful, and potentially confusing parts of any PC. The BIOS keeps track of the most integral system settings, and serves as a sort of preflight check when you first boot -- ensuring that your hardware is working properly, and adjusting your system profile and informing the operating system if any new components have been added. It also plays a vital role in CPU performance. This article will present the BIOS basics you need to know before considering any system upgrade. BIOS and CMOS Stored as firmware in a memory chip, the BIOS program reads -- and, when changes are made, writes or updates -- the system configuration info stored in a CMOS (complementary metal oxide semiconductor) RAM chip on the motherboard. A small lithium battery (which usually lasts for years) lets the low-power CMOS chip store configuration settings and the system date and time even when the PC's turned off. (Though it's not technically correct, the acronyms are often used interchangeably; i.e., the utility that lets you make changes is referred to as both a "BIOS setup screen" and "CMOS setup screen.") At startup, the BIOS uses the stored settings and its own programming to identify the available hardware -- the CPU, memory size and speed, disk drives, and so on. A power-on self-test (POST) tests the RAM and other hardware and warns of any changes, inconsistencies, or problems. Once the BIOS has finished its job, the computer is essentially a blank slate that allows any compatible operating system to be loaded -- Windows XP, Linux, or an old DOS boot disk you've got lying around. Since the BIOS initializes the hardware, there doesn't even have to be an operating system per se; some newer motherboards have a nifty feature that can play music CDs right after the BIOS loads. This illustrates how versatile a PC can be, as the BIOS is like an open door to allow virtually any subsequent software to work with the installed hardware. Usually, of course, you're using a conventional operating system; once the OS loads, most BIOS functions fade into the background. Since Windows 95, Plug and Play technology has done a lot to minimize resource allocation to the system BIOS, as the operating system takes control of the resident hardware and takes over the job of recognizing peripherals added later (i.e., those that need not be active at boot time, like a digital camera plugged into a USB port). Entering the BIOS and Editing Your Configuration We should say up front that the vast majority of users will never need to fool around in the BIOS. CPU and memory upgrades, operating system refreshes, and new external peripherals are all reasons for BIOS/CMOS adjustment, but today's BIOS routines' high level of auto-detect features will handle most alterations. If your system is running well, repeat after us: If it ain't broke, don't fix it. In the event that BIOS settings do need to be adjusted, you usually initiate the process by pressing a key during startup. The key used varies from system to system, with Delete, Esc, F2, and F10 among the popular choices; often a "Press [your key here] to enter Setup" message flashes on the screen for a few seconds at boot time. Due to user support and warranty issues, some system manufacturers have implemented relatively hidden or disabled BIOS setup programs, and a bit more detective work may be required to access these. One last warning: When it comes to changing any BIOS setting, prepare for the worst -- a frozen or unbootable PC -- and have a rescue plan. Most motherboards offer another keystroke option to reset the BIOS and enable a boot with default settings. In the realm of worst-case scenarios, there's a physical jumper on the motherboard that can perform the reset (as always, power off before messing with motherboard components), or you can resort to the tried-and-true method of removing and then reinserting the CMOS battery before turning the system back on.