Mike Meyers A+ Guide to Managing and Troubleshooting Pcs Instructor S Manual Chapter 5

Mike Meyers’ A+ Guide to Managing and Troubleshooting PCs Instructor’s ManualChapter 5

Chapter 5

BIOS and CMOS

Learning Objectives

In this lesson,you will learn how to identify various BIOS types, understand how the BIOS functions, configure the CMOS setup utility options, describe the BIOS device drivers, and troubleshoot POST and CMOS. By the end of this lessonyou should be able to do the following:

Explain the function of BIOS
Describe BIOS and device drivers
Distinguish among various CMOS setup utility options
Troubleshoot the Power-On Self Test (POST)

Pre-test

1.Describe the function of the basic input/output services (BIOS).

2.Describe the function of the complementary metal-oxide semiconductor (CMOS).

3.The desktop clock losing time is a symptom of what?

4.Name a common method to enter the setup program.

5.What is it called when you update the BIOS?

Lecture Outline

Historical/Conceptual

I.We Need to Talk

A.Two functions are necessary for devices to work:

1.CPU must have a way to talk to devices.

2.Devices must have a way to send data to and receive data from the CPU.

B.Northbridge, the first chip in the chipset, connects the CPU to video and/or memory.

C.Southbridge, the second chipset chip, handles all inputs and outputs to the many devices in the PC and extends data bus and address bus to all other parts of PC.

D.Basic input/output system (BIOS) holds the programming code that allows the CPU to communicate with the rest of the system.

1.BIOS held in read-only memory (ROM).

E.Talking to the keyboard

1.Example: how the CPU recognizes when a key is pressed.

a)A keyboard controller chip (now part of the Southbridge) recognizes when a key is pressed.Let’s say the A was pressed.

b)The keyboard controller reads the data and looks it up in its “code book” to determine what key is pressed.

c)The keyboard controller then gets the attention of the CPU, essentially saying, “I have some data.”

d)When the CPU addresses the keyboard controller, the keyboard controller places the data onto the external data bus so that the CPU can read it.

e)For all of this to work, programming has to be readily available to the CPU and the keyboard controller as soon as it is powered up.This programming is stored in ROM.

Discussion Point

Putting it together

In the first few chapters, various components were discussed, including address buses, data buses, RAM, CPUs, chipsets, support chips, caches, input devices, storage devices, and output devices. The BIOS is simply a group of programs stored in a secure place (a ROM chip) that serves asthe basic instruction code to control all that hardware.

F.Read-only memory (ROM) chip also called system ROM or the ROM BIOS.

1.Non-volatile (does not lose its programming, even if no power)

2.Read-only means it cannot be easily erased

3.Stores hundreds of programs referred to as basic input/output services (BIOS)

4.ROM BIOS typically holds 64KB (65,536) lines of data code, though current Flash ROM is often 2MB or more in size

5.Historicallya DIPP chip with a shiny label on it, but has gone through many changes

E.Each time the CPU needs to talk to a component, it refers to the BIOS for the program to talk to that specific device.

F.The CPU talks to the ROM BIOS the same way it talks to RAM—through the address bus—with some of the address bus being reserved for the ROM BIOS.

G.Many devices and expansion cards have their communication programs on ROM chips.

Discussion Point

Software and firmware

Programs that typically reside in RAM or on other erasable media are called software, while programs that reside in ROM are called firmware.Compare this to devices and chips that you can physically touch, which is referred to as hardware.

Essentials

II.Complementary metal-oxide semiconductor (CMOS)

A.What it is

1.A separate chip from the ROM BIOS

2.Volatile: kept alive by a battery

3.Also acts as a clock and keeps the date and time

4.Stores only the changeable data, not programs, read by the BIOS

5.Customizable via setup program. Setup program is stored on the ROM BIOS, but the customizable settings are on the CMOS chip

6.Stores semi-permanent, user-changeable data related to hardware components such as disk drives, RAM, and I/O ports

7.Is typically 64KB, but only a fraction of that is actually used to store the critical data

III. CMOS Setup Utilities

Discussion Point

BIOS manufacturers

In 1998, Phoenix and Award merged as Phoenix. However, Phoenix still markets Phoenix and Award BIOS separately.

A.Updating CMOS: The Setup program

1.The CMOS setup program is built into the system ROM chip and may be accessed in a number of ways, depending on the manufacturer and date of the ROM chip.

a)Many BIOS manufacturers. Each manufacturer uses a different key sequence to enter the CMOS setup and may use a different key sequence within different models of the same brand.

b)The most common BIOS manufacturers and some common key sequences to enter the CMOS Setup (usually says on the boot screen) are

(1)Award (most common): Pressdel

(2)Phoenix: Press ctrl-alt-esc or f2

(3)American Megatrends (AMI): Pressdel

(4)Forothers pressf1, ctrl-alt-ins,ctrl-alt-enter, or ctrl-alt-s

B.A quick tour of a typical CMOS setup (Award)

1.CPU soft menu: Found on newer “jumperless” motherboards; controls things like voltages and multipliers. Normally, you would keep these settings at AUTO.

2.Advanced BIOS settings: Boot option, as well as other miscellaneous items usually found here.

3.Advanced chipset features: Deals with low-level chipset functions. Normally, you would leave settingshere at their default values.

4.Integrated peripherals: Used to configure ports.

5.Power management: Used to set sleep timers method. Also often used to configure IRQs (Enabled/Disabled/AUTO).

6.PnP/PCI configuration: Set up plug-and-play configurations and also sometimes IRQ settings.

7.PC Health Status.

8.Set Password: Set user password (a password to boot the computer) or an administrator password (to get into CMOS).

9.EXIT: Save or not save the changes made to the CMOS.

Discussion Point

CMOS options

A typical CMOS setup has tons of options you can adjust. Few techs, if any, know what they all mean. Basically, if it is not covered in the text, it is probably not critical to the PC function and it probably is not on the CompTIA A+ Certification exam. Leaving those settings at their default values is usually fine.

Discussion Point

Modern CMOS

In the newer version of motherboards, the CMOS chip is being phased out. Since the advent of Flash ROM, the PROM chip now has the ability to store the CMOS data within itself, eliminating the need for a separate CMOS chip.

IV.Option ROM and Device Drivers

A.Option ROM or Bring your own BIOS (BYOB)

1.Individual ROM BIOS on expansion cards and devices

2.Device drivers loaded into RAM at boot

B.Device drivers—file stored on the hard drive that loads all the BIOS commands for a specific device into RAM at boot

1.Comes with a device you buy as an installation discs (floppy or CD-ROM)

C.BIOS, BIOS, everywhere

1.Every piece of hardware must have a program that allows the CPU to communicate with it.

a)Program may be on motherboard ROM

b)Program may be on ROM on the individual hardware

c)Program may be on a driver

d)Program may be loaded into RAM at boot

IT Technician

V.Power-On Self Test (POST)

A.Upon boot, the ROM initiates the POST process

1.The POST routine sends out a message to all assumed components to initiate self tests. This determines whether or not the components are working properly.Quality of POST diagnostic determined by component.

2.If a component fails self diagnostics, the POST process halts and sends an error message.

Before and during the video test: beep codes
If video is missing or faulty, you’ll hear one long beep followed by three short beeps.
If RAM is missing or faulty, you’ll hear a rather alarming buzzing that will repeat as long as the computer is on.
If POST completes successfully, you’ll hear one or two short beeps.

C.Text errors

1.Once the video is determined to be good, errors can be displayed.

2.Errors are usually displayed in clear text, though they can sometimes be rather cryptic.

D.POST cards

1.The small expansion card installs into an available slot.

2.Note the light emitting diode (LED) display to see what device POST is currently checking. Refer to the two-digit hex code on the LED display to determine the faulty POST code.

3.Look up the code in the companion manual. It can help identify the faulty component.

4.If the PC passes POST, the problem is more likely a software problem.

Discussion Point

Beep codes and POST codes

Each BIOS manufacturer sets the beep codes to its own internal needs. Different versions of BIOS from the same manufacturer can have different beep codes. The same thing goes for POST codes when using a POST card. Each BIOS version responds with a different two-digit hex code for a specific error.

Discussion Point

Diagnostic tip

If you are receiving intermittent beep codes or POST codes, try turning the power on and off several times and see if the same code comes up each time. If it is not the same code each time, the problem might be the power supply.

E.The boot process

1.CPU “wakes up” and checks for proper voltage. If proper voltage is found, CPU sends a built-in memory address, which is the first line of the POST program on the system ROM.

2.The ROM begins the POST routines.

3.Once POST is passed, the ROM begins the boot process (the bootstrap loader) by looking for an operating system according to the CMOS settings.

4.The CMOS settings tell it which device to try to boot from.It looks at the boot sector of that device (floppy, CD-ROM, hard drive, etc.) and tries to load an operating system.

5.Once the boot process begins, control is handed over to the operating system.

VI.Care and feeding of BIOS and CMOS.

A.Losing CMOS settings

1.Battery provides continuous trickle charge to hold data.Also keeps clock running

2.If battery dies or is removed, all data is lost and system returns to factory defaults

3.Common errors

a)CMOS configuration mismatch

b)CMOS date/time not set

c)No boot device available

d)CMOS battery state low

4.Common reasons for losing CMOS data

a)Pulling and inserting cards

b)Touching the motherboard

c)Dropping something on the motherboard

d)Dirt on the motherboard

e)Faulty power supplies

f)Electrical surges

g)Chip creep

Discussion Point

Chip/boardcreep

PCs repeatedly get hot and cold, causing components to expand and contract regularly.Chips that are just plugged into a socket can work their way out of socket due to this process.Most chips today are soldered in to prevent this problem.
A similar concept is board creep.Due to the same hot and cold, expansion and contraction, boards that are not secured in their slots will slowly work their way out.

5.If settings keep resetting, replace the battery

B.Clearing CMOS

1.CMOS has a failsafe on the motherboard.If you need to clear it to factor settings, use the jumper or shunt to send a reset single to the CMOS.

2.Useful if overzealous tech has changed one thing too many without normalizing.

3.Useful if overzealous user has password protected the BIOS but forgot the password.

C.Flashing ROM

1.Flash ROM chips can be reprogrammed.

2.Download the program from manufacturer and follow instructions.

3.Typically load onto floppy and boot from floppy.

4.Only flash the BIOS if necessary.