1. BIOS
Chapter 8

2. Overview In this chapter, you will learn how to
Explain the function of BIOS
Distinguish among various CMOS setup utility options
Describe option ROM and device drivers
Troubleshoot the power-on self test (POST)
Maintain BIOS and CMOS properly 2

3. We need to talk…
A group of disjointed parts is not very useful. They need to be able to talk to each other to be useful. 3

4. Necessary CPU Functions
Two functions are necessary for devices to work:
The CPU must have a way to talk to devices.
Devices must have a way to send data to and receive data from the CPU.
Fix: We’ll elevate the MCC into the chipset and use that to connect the CPU to all the devices.

5. The Northbridge and Southbridge
The Northbridge is the first chip in the chipset.
Connects the CPU to video and/or memory
The Southbridge, the second in the chipset
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.
The chipset extends the data bus to touch all the devices.
It also extends the address bus.
Note: Modern processors include the functions of the Northbridge directly on the CPU. The Southbridge is now called the Input/Output Controller Hub (ICH) in new Intel systems and the Fusion Controller Hub (FCH) in new AMD systems.

6. The Northbridge and Southbridge (continued)
The MCC isn’t just the memory controller anymore, so let’s now call it the Northbridge because it acts as the primary bridge between the CPU and the rest of the computer (see Figure 1).
Figure 1: Meet the Northbridge

7. The Northbridge and Southbridge (continued)
The chipset extends the data bus to every device on the PC. The CPU uses the data bus to move data to and from all of the devices of the PC. Data constantly flows on the external data bus among the CPU, chipset, RAM, and other devices on the PC (see Figure 2).
Figure 2: The chipset extending the data bus

8. The Northbridge and Southbridge (continued)
The first use for the address bus, as you know, is for the CPU to tell the chipset to send or store data in memory and to tell the chipset which section of memory to access or use. Just as with the external data bus, the chipset extends the address bus to all of the devices (see Figure 3). That way, the CPU can use the address bus to send commands to devices, just as it sends commands to the chipset.
Figure 3: Every device in your computer connects to the address bus.

9. Talking to the Keyboard
Example: how the CPU recognizes when a key is pressed
A keyboard controller chip (now part of the Southbridge) recognizes when a key is pressed. Let’s say the “J” key was pressed.
The keyboard controller scans the matrix of wires on the keyboard and puts the scan code for the “J” key into its register.
The keyboard controller then gets the attention of the CPU, essentially saying, “I have some data.”
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.
But how does the CPU tell the 8042 to put the contents of its register on the data bus? The CPU uses the keyboard controller’s codebook!

10. Talking to the Keyboard (continued)
Example: how the CPU recognizes when a key is pressed (continued)
For all of this to work, programming has to be readily available to the CPU, and the CPU needs this programming as soon as it is powered up—this programming is stored in ROM.
The keyboard controller was one of the last single-function chips to be absorbed into the chipset. For many years—in fact, well into the Pentium III/ Early Athlon era—most motherboards had separate keyboard controller chips. Figure 4 shows a typical keyboard controller from those days. Electronically, it looked like Figure 5. Even though the model numbers changed over the years, you’ll still hear techs refer to the keyboard controller as the 8042, after the original keyboard controller chip.
Figure 4: A keyboard chip on a Pentium motherboard
Figure 5: Electronic view of the keyboard controller

11. Talking to the Keyboard (continued)
Every time you press a key on your keyboard, a scanning chip in the keyboard notices which key you pressed. Then the scanner sends a coded pattern of ones and zeros—called the scan code—to the keyboard controller. Every key on your keyboard has a unique scan code. The keyboard controller stores the scan code in its own register. Does it surprise you that the lowly keyboard controller has a register similar to a CPU? Lots of chips have registers—not just CPUs (see Figure 6).
Figure 6: Scan code stored in keyboard controller’s register

12. Talking to the Keyboard (continued)
How does the CPU get the scan code out of the keyboard controller (see Figure 7)? While we’re at it, how does the CPU tell the keyboard to change the typematic buffer rate (when you hold down a key and the letter repeats) or to turn the number lock LED on and off, to mention just a few other jobs the keyboard needs to do for the system? The point is that the keyboard controller must be able to respond to multiple commands, not just one.
Figure 7: The CPU ponders the age-old dilemma of how
to get the 8042 to cough up its data.

13. BIOS (Basic Input/Output Services)
The read-only memory (ROM) chip also called system ROM or the ROM BIOS
Nonvolatile (does not lose its programming, even if no power)
Read-only means it cannot be easily erased
Stores hundreds of programs called services; collectively, this is the basic input/output services or system (BIOS)
System ROM typically holds 64KB (65,536) lines of data code, though current Flash ROM is often 2 MB or more in size
Historically, a DIPP chip with a shiny label on it, but it has gone through many changes

14. BIOS (continued)
Each time the CPU needs to talk to a component, it refers to the BIOS for the program to talk to that specific device.
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.
Many devices and expansion cards have their communication programs on ROM chips.

15. Figure 8: Typical flash ROM
BIOS (continued)
Modern motherboards use a type of ROM called flash ROM that differs from traditional ROM in that you can update and change the contents through a very specific process called “flashing the ROM,” covered later in this chapter. Figure 8 shows a typical flash ROM chip on a motherboard.
Figure 8: Typical flash ROM

16. Figure 9: Function of the flash ROM chip
BIOS (continued)
Every motherboard has a flash ROM chip, called the system ROM chip because it contains code that enables your CPU to talk to the basic hardware of your PC (see Figure 9).
Figure 9: Function of the flash ROM chip

17. Figure 10: CPU running BIOS service
BIOS (continued)
The hundreds of little programs stored on the system ROM chip on the motherboard are called, collectively, the system BIOS (see Figure 10). Techs call programs stored on ROM chips of any sort firmware.
Figure 10: CPU running BIOS service

18. Complementary Metal-Oxide Semiconductor (CMOS)
What it is:
A separate chip from the ROM BIOS, though most often now part of the Southbridge
Volatile: kept alive by a battery
Also acts as a clock and keeps the date and time
Stores only the changeable data, not programs, read by the BIOS
Customizable via setup program. The setup program is stored on the ROM BIOS, but the customizable settings are on the CMOS chip.
Stores semipermanent, user-changeable data related to hardware components such as disk drives, RAM, and I/O ports

19. Complementary Metal-Oxide Semiconductor (CMOS) (continued)
What it is (continued):
Is typically 64 KB, but only a fraction of that is actually used to store the critical data
Years ago, CMOS was a separate chip on the motherboard, as shown in Figure 11. Today, the CMOS is almost always built into the Southbridge.
Figure 11: Old-style CMOS

20. Modify CMOS: The Setup Program
PCs come with CMOS setup programs
Allows you to access and modify CMOS data
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.
There are 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

21. Modify CMOS: The Setup Program (continued)
Figure 13: Award/Phoenix BIOS information
Figure 12: AMI BIOS information
Every PC ships with a program built into the system ROM called the CMOS setup program or the system setup utility that enables you to access and modify CMOS data. When you fire up your computer in the morning, the first thing you likely see is the BIOS information. It might look like the example shown in Figure 12 or perhaps like the example shown in Figure 13.

22. Modify CMOS: The Setup Program (continued)
The most common BIOS manufacturers and some common key sequences to enter the CMOS Setup (usually says on the boot screen) are:
Award (most common): Press DEL
Phoenix: Press CTRL-ALT-ESC or F2
American Megatrends (AMI): Press DEL
For others press F1, CTRL-ALT-INS, CTRL-ALT-ENTER, or CTRL-ALT-S

23. Modify CMOS: The setup Modify CMOS: The Setup Program (continued) (continued)
Figure 15: Standard CMOS Features screen
Figure 14: Typical CMOS main screen by Award
As an example, let’s say your machine has Award BIOS. You boot the system and press DEL to enter CMOS setup. The screen shown in Figure 14 appears. If you select the Standard CMOS Features option, the Standard CMOS Features screen appears (see Figure 15).

24. Modify CMOS: The Setup Program (continued)
Figure 17: Older Award setup screen
Figure 16: Phoenix BIOS CMOS setup utility Main screen
Figure 16 shows the same standard CMOS setup screen on a system with Phoenix BIOS. Note that this CMOS setup utility calls this screen “Main.”
Compare the older Award screen in Figure 17 with the more modern Award CMOS screen in Figure 14. Figure 17 looks different—and it should—as this much older system simply doesn’t need the extra options available on the newer system.

25. Modify CMOS: The Setup Program (continued)
MB Intelligent Tweaker (M.I.T.):
You can use the MB Intelligent Tweaker (M.I.T.) to change the voltage and multiplier settings on the motherboard for the CPU from the defaults.
Motherboards that cater to overclockers tend to have this option.
Normally, you would keep these settings at AUTO or default.

26. Modify CMOS: The Setup Program (continued)
You can use the MB Intelligent Tweaker (M.I.T.) to change the voltage and multiplier settings on the motherboard for the CPU from the defaults. Motherboards that cater to overclockers tend to have this option. Usually you just set this to Auto or Default and stay away from this screen (see Figure 18).
Figure 18: MB Intelligent Tweaker (M.I.T.)

27. Modify CMOS: The Setup Program (continued)
Advanced BIOS Features: Boot option, as well as other miscellaneous items usually found here
Virtualization Support: A virtual machine is a powerful type of program that enables you to run multiple software-based machines inside your physical PC
Recreates (or virtualizes) the motherboard, hard drives, RAM, network adapters, and more, and is just as powerful as a real PC
To run these virtual machines, you need a very powerful PC—CPU manufacturers have added hardware-assisted virtualization

28. Modify CMOS: The Setup Program (continued)
Advanced BIOS Features is the dumping ground for all of the settings that aren’t covered in the Standard menu and don’t fit nicely under any other screen. This screen varies wildly from one system to the next. You most often use this screen to select the boot options (see Figure 19).
Figure 19: Advanced BIOS Features

29. Modify CMOS: The Setup Program (continued)
Advanced BIOS Features (continued):
Chassis Intrusion Detection: When enabled, it is used to warn an administrator if someone has opened the case. Often a hardware switch and a BIOS setting are used to detect an intrusion
Advanced chipset features: Deals with low-level chipset functions
Normally, you would leave settings here at their default values
Integrated peripherals: Used to configure ports

30. Modify CMOS: The Setup Program (continued)
The Advanced Chipset Features screen (see Figure 20) strikes fear into most everyone, because it deals with extremely low-level chipset functions. Avoid this screen unless a high-level tech (such as a motherboard maker’s support tech) explicitly tells you to do something in here.
Figure 20: Advanced Chipset Features

31. Modify CMOS: The Setup Program (continued)
You will use the Integrated Peripherals screen quite often. Here you configure, enable, or disable the onboard devices, such as the integrated sound card (see Figure 21).
Figure 21: Integrated Peripherals

32. Modify CMOS: The Setup Program (continued)
Power management setup:
Used to set the sleep timers method. Also often used to configure IRQs (Enabled/Disabled/AUTO)
Overclocking:
Many PCs have CMOS setup menus that display information about the CPU, RAM, and GPU and include controls for overclocking them
PnP/PCI configuration:
Set up plug-and-play configurations and also sometimes IRQ settings

33. Modify CMOS: The Setup Program (continued)
Figure 23: PnP/PCI Configurations
Figure 22: Power Management Setup
As the name implies, you can use the Power Management Setup screen (see Figure 22) to set up the power management settings for the system.
Figure 23: Plug and play (PnP) is how devices automatically work when you snap them into your PC.

34. Modify CMOS: The Setup Program (continued)
And the rest of the CMOS settings:
PC Health Status: Often display information about voltage, CPU and case temperatures, and fan speed
Load Fail-Safe: These options reset all settings to their fail-safe or factory default settings. Generally used when a setting prevents a system from booting or to fix corrupt settings
Optimized: Sets CMOS settings for the best possible speed/stability
Set Password: Set user password (a password to boot the computer) or an administrator password (to get into CMOS)

35. Modify CMOS: The Setup Program (continued)
Many CMOS setup programs enable you to set a password in CMOS to force the user to enter a password every time the system boots. Don’t confuse this with the Windows logon password. This CMOS password shows up at boot, long before Windows even starts to load. Figure 24 shows a typical CMOS password prompt.
Figure 24: CMOS password prompt

36. Modify CMOS: The Setup Program (continued)
And the rest of the CMOS settings (continued):
DriveLock passwords: Enables an ATA security feature that prevents unauthorized access to a hard drive. A password is required to boot.
Some PC manufacturers also include LoJack security features in their BIOS—this way, if your PC is stolen, you can track its location, install a key logger, or even remotely shut down your computer.

37. Modify CMOS: The Setup Program (continued)
And the rest of the CMOS settings (continued):
Trusted Platform Module (TPM): Acts as a cryptoprocessor for various encryption technologies such as Digital Rights Management (DRM), disk encryption, network access control, application execution control, and password protection
Exiting and saving settings: Saves or doesn’t save the changes made to the CMOS

38. Option ROM and Device Drivers
Option ROM or Bring your own BIOS (BYOB)
Individual ROM BIOS on expansion cards and devices
Device drivers loaded into RAM at boot
Device drivers—each a file stored on the hard drive that loads all the BIOS commands for a specific device into RAM at boot
Comes with a device you buy as an installation disc (floppy or CD-ROM)

39. Option ROM and Device Drivers (continued)
The first way to BYOB is to put the BIOS on the hardware device itself. Look at the card displayed in Figure 25. This is a serial ATA RAID hard drive controller—basically just a card that lets you add more hard drives to a PC. The chip in the center with the wires coming out the sides is a flash ROM that stores BIOS for the card. The system BIOS does not have a clue about how to talk to this card, but that’s okay, because this card brings its own BIOS on what’s called an option ROM chip.
Figure 25: Option ROM

40. Option ROM and Device Drivers (continued)
Figure 27: Windows asking for the installation disc
Figure 26: Option ROM at boot
Most BIOS that come on option ROMs tell you that they exist by displaying information when you boot the system. Figure 26 shows a typical example of an option ROM advertising itself.
In most cases, you install a new device, start the computer, and wait for Windows to prompt you for the installation disc (see Figure 27).

41. Option ROM and Device Drivers (continued)
BIOS, BIOS, everywhere
Every piece of hardware must have a program that allows the CPU to communicate with it
The program may be on motherboard ROM
The program may be on ROM on the individual hardware
The program may be on a driver

42. Power-on self-test (POST)

43. ROM Initiates the POST Process
Upon boot, the ROM initiates the POST process
The POST routine sends out a message to all assumed components to initiate self-tests
This determines whether the components are working properly. The quality of POST diagnostics is determined by the component.
If a component fails self-diagnostics, the POST process halts and sends an error message.

44. Beep Codes 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 beeping/buzzing that will repeat as long as the computer is on.
If the POST completes successfully, you’ll hear one or two short beeps.

45. Figure 28: POST text error messages
Text Errors
Once the video is determined to be good, errors can be displayed.
Errors are usually displayed in clear text, though they can sometimes be rather cryptic.
After the video has tested okay, any POST errors display on the screen as text errors. If you get a text error, the problem is usually, but not always, self-explanatory (see Figure 28). Text errors are far more useful than beep codes, because you can simply read the screen to determine the bad device.
Figure 28: POST text error messages

46. POST Cards The small expansion card installs into an available slot
used to monitor the POST and identify whether a piece of hardware is causing startup issues
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
Look up the code in the companion manual—it can help identify the faulty component

47. POST Cards (continued)
If the PC passes POST, the problem is more likely a software problem
POST cards used to be an essential tool for techs
Today they are rarely used, and then only on a “dead” PC to determine at which level it’s dead
If the POST card shows no reading, the problem is before the POST and must be related to the CPU

48. POST Cards (continued)
A small, two-character light-emitting diode (LED) readout on the card indicates which device the POST is currently testing (see Figure 29).
Figure 29: POST card in action

49. The Boot Process The power supply checks for proper voltage.
If the proper voltage is found, the power supply sends a signal through the power good wire.
This awakens the CPU, which in turn sends a built- in memory address, which is the first line of the POST program on the system ROM.
The ROM begins the POST routines.
Once the POST is passed, the ROM begins the boot process (the bootstrap loader) by looking for an operating system according to the CMOS settings.

50. The Boot Process (continued)
Figure 30: CMOS boot order
Your PC’s CMOS setup utility has an option that you configure to tell the bootstrap loader which devices to check for an operating system and in which order (see Figure 30).

51. The Boot Process (continued)
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.
Once the boot process begins, control is handed over to the operating system.
Some BIOS allow the PC to use a preboot execution environment (PXE).
A PXE enables you to boot a PC without any local storage by retrieving an OS from a server over a network.

52. Care and feeding of BIOS and CMOS

53. Losing CMOS Settings
The battery provides continuous trickle charge to hold data. It also keeps the clock running.
If the battery dies or is removed, all data is lost and the system returns to factory defaults.
Common errors
CMOS configuration mismatch
CMOS date/time not set
No boot device available
CMOS battery state low

54. Losing CMOS Settings (continued)
Common reasons for losing CMOS data
Pulling and inserting cards
Touching the motherboard
Dropping something on the motherboard
Dirt on the motherboard
Faulty power supplies
Electrical surges
If settings keep resetting, replace the battery.

55. Losing CMOS Settings (continued)
Your CMOS needs a continuous trickle charge to retain its data. Motherboards use some type of battery, usually a coin battery like those in wrist watches, to give the CMOS the charge it needs when the computer is turned off (see Figure 31). This battery also keeps track of the date and time when the PC is turned off.
Figure 31: A CMOS battery

56. Flashing ROM Flash ROM chips can be reprogrammed.
Download the program from the manufacturer and follow instructions.
Typically insert a removable disk of some sort (usually a USB thumb drive) containing an updated BIOS file.
Only flash the BIOS if necessary.

57. Flashing ROM (continued)
Figure 32: ROM -updating program for an ASUS motherboard

58. Beyond A+

59. UEFI
BIOS hasn’t changed much since it was conceived back in the 1980s.
BIOS works only in 16-bit mode and depends on x86-compliant hardware.
In addition, if there is more than one operating system loaded on a single drive, you need one of those installed OSes to act as a boot loader.
In 2005, Intel released its Extensible Firmware Interface (EFI) for public standards, creating the Unified EFI forum to manage the specification.
Became the Unified Extensible Firmware Interface (UEFI)

60. UEFI (continued)
UEFI acts as a super-BIOS, doing the same job in a 64-bit environment.
UEFI:
Supports 32-bit or 64-bit booting
Handles all boot-loading duties
Is not dependent on x86 firmware
UEFI motherboards only became available in 2011 due to limitations of older BIOS to handle larger MBR partition support (>2.2 TB)
3 TB drives had issues with older BIOS

61. UEFI (continued)
UEFI motherboards support booting a newer type of hard drive partitioning called GUID Partition Table (GPT)
Supports partitions larger than 2.2 TB

62. UEFI (continued)
As 3-TB and larger drives began to appear in 2011, people using traditional BIOS discovered that strange issues popped up when they wanted to boot off of a 3-TB hard drive (see Figure 33). Instead of a 3-TB volume, you’d find a 2.2-TB volume and unpartitioned space.
Figure 33: Here’s what happens when you install Windows 7
on a greater-than-2.2-TB drive using regular BIOS.

63. UEFI (continued)
UEFI motherboards support booting a newer type of hard drive partitioning called GUID Partition Table (GPT) that supports partitions larger than 2.2 TB. If you want to boot off of a hard drive using a single partition greater than 2.2 TB, you must use a UEFI motherboard and the hard drive must be blank. If your system meets these two criteria, the Windows 7 installation routine will automatically make a GPT drive for you (see Figure 34).
Figure 34: Here’s what happens when you install Windows 7
on a greater-than-2.2-TB drive using UEFI.

64. UEFI (continued) Figure 36: POST and system setup are still here.
Although the EFI folks clearly defined issues such as booting and accessing firmware, they didn’t define issues such as the graphical user interface or audio. If you think UEFI possesses a standard interface similar to the Windows desktop, forget it. Figure 35 shows an ASUS motherboard’s UEFI interface. UEFI serves as a non-hardware-specific, non-OS-specific, 32- or 64-bit bootloader. This doesn’t make things like POST or system setup go away. They still exist, but now UEFI runs the show instead of BIOS (see Figure 36).
Figure 35: ASUS EFI BIOS Utility