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BIOS and CMOS

BIOS and CMOS

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BIOS and CMOS

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    1. BIOS and CMOS Chapter 4

    2. Overview In this chapter, you will learn to Explain the function of BIOS Distinguish among various CMOS setup utility options Describe BIOS and device drives Troubleshoot the Power-On Self Test (POST) Instructor Tip When gaining attention and establishing common ground, ask questions of the class such as, Who here knows what BIOS is? or Who can identify the BIOS chip on the motherboard? For a positive statement, tell the class, In this lesson, we are going to see how to use, configure, and maintain the BIOS.Instructor Tip When gaining attention and establishing common ground, ask questions of the class such as, Who here knows what BIOS is? or Who can identify the BIOS chip on the motherboard? For a positive statement, tell the class, In this lesson, we are going to see how to use, configure, and maintain the BIOS.

    3. The Function of BIOS

    4. Northbridge & Southbridge Northbridge Chip or chips that connect the CPU to memory, the PCI bus, Level 2 cache and AGP activities Northbridge chips communicate with the CPU thru the Frontside Bus Southbridge Handles all of the inputs and outputs to the many devices in the PC A chipset is a set of Northbridge and Southbridge chips that work together Tech Tip Chipset Architecture The workload of the two chips that make up the chipset in modern PCs varies according to manufacturer and model. The distinctions drawn here Northbridge for RAM, Southbridge for devicesworks for most chipsets designed for the Pentium, Pentium Pro, and Pentium II processors, and the latest and greatest Athlon XP. The Northbridge for the Pentium 4, in contrast, handles all the PCI devices in addition to RAM. Chipset makers rarely use the terms Northbridge and Southbridge anymore, but because most modern chipsets consist of only two or three chips with basically the same functions, techs continue to use the terms. Tech Tip Chipset Architecture The workload of the two chips that make up the chipset in modern PCs varies according to manufacturer and model. The distinctions drawn here Northbridge for RAM, Southbridge for devicesworks for most chipsets designed for the Pentium, Pentium Pro, and Pentium II processors, and the latest and greatest Athlon XP. The Northbridge for the Pentium 4, in contrast, handles all the PCI devices in addition to RAM. Chipset makers rarely use the terms Northbridge and Southbridge anymore, but because most modern chipsets consist of only two or three chips with basically the same functions, techs continue to use the terms.

    5. The Bus The external data bus joins the various parts of the PC together The address bus also connects to various parts

    6. Talking to the Keyboard The keyboard talks to the external data bus using the keyboard controller chip (8042) The Southbridge chip handles the keyboard interface, acting as the keyboard controller chip among its many other functions. Manufacturers today choose a specific chipset, rather than an individual keyboard controller. The Southbridge chip handles the keyboard interface, acting as the keyboard controller chip among its many other functions. Manufacturers today choose a specific chipset, rather than an individual keyboard controller.

    7. BIOS A special kind of program is required to enable the CPU to talk to other devices A ROM chip stores these programs These programs are collectively known as the Basic Input/Output Service (BIOS) Discussion Point Putting It Together Recall from the first few chapters, we discussed various components, 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 is the basic instruction code to control all that hardware. The ROM chip on the motherboard that holds the System BIOS is called the System ROM, or ROM BIOS. Discussion Point Putting It Together Recall from the first few chapters, we discussed various components, 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 is the basic instruction code to control all that hardware. The ROM chip on the motherboard that holds the System BIOS is called the System ROM, or ROM BIOS.

    8. BIOS Each program is called a service Programs stored on ROM chips are known as firmware Programs stored on erasable media are called software 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.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.

    9. BIOS BIOS and its relation to memory addressing: The wire pattern generated by the address bus is called the address space The BIOS stored on the ROM chip attached to the motherboard is called the system BIOS The ROM chip that stores the system BIOS is called the system ROM

    10. BIOS Where is the BIOS stored? The last 65,536 addresses on the address bus are reserved for the BIOS on the ROM chip But there are many other devices that have a BIOS chip, so 384K of the first megabyte of memory is always reserved for the various BIOS chips Where is the BIOS stored? The last 65,536 addresses on the address bus are reserved for the BIOS on the ROM chip But there are many other devices that have a BIOS chip, so 384K of the first megabyte of memory is always reserved for the various BIOS chips

    11. Core Group of Hardware Hardware that is common, necessary and never changes Keyboard, speaker Stored on the system BIOS chip

    12. CMOS Group of Hardware Hardware that is common, necessary but may change RAM, hard drives, floppy drives, serial and parallel ports Complementary metal-oxide semiconductor Programs are stored on the system BIOS chip, while the changeable data is stored on a CMOS chip

    13. CMOS Setup Utilities

    14. The CMOS Setup Program The data on the CMOS chip can be accessed and updated via the CMOS setup program. American Megatrends (AMI), Award software, and Phoenix Technologies are the main manufacturers of BIOS. The CMOS setup can be accessed when the system boots, but there are different ways of doing that Discussion Point BIOS Manufacturers A few years back, Phoenix and Award merged as Phoenix. However, Phoenix still markets Phoenix and Award BIOS separately.Discussion Point BIOS Manufacturers A few years back, Phoenix and Award merged as Phoenix. However, Phoenix still markets Phoenix and Award BIOS separately.

    15. Accessing the CMOS AMI and Award Press DEL Phoenix Press Ctrl-Alt-Esc or F2

    16. CMOS Setup The floppy drive, hard drive, and the date/time settings can be changed using the standard CMOS setup Modern computers provide extra CMOS settings for memory management, password and booting options, error handling, and power management

    17. CMOS Setup Note Not all Award CMOS setups will have the same pages as those listed here.Note Not all Award CMOS setups will have the same pages as those listed here.

    18. CMOS Setup The following CMOS setting options are available: CPU soft menu Enables you to set the voltage and multiplier settings on the motherboard for the CPU. Advanced BIOS feature Used for selecting boot options. Advanced chipset features Deals with extremely low-level chipset functions.

    19. CMOS Setup The following CMOS setting options are available (continued): Integrated peripherals Allows you to configure, enable, or disable onboard ports. Power management setup Used to setup power management settings for the system. PnP/PCI configurations Used for assigning IRQs to certain resources.

    20. CMOS Setup Other options include: Load Fail-Safe Defaults: used when low-level problems occur Load Optimized Defaults: sets the CMOS to the best possible speed and stability of the system Set Password Save and Exit Setup Exit Without Saving

    21. Soft Menu

    22. Standard CMOS Features

    23. Advanced BIOS Features

    24. Advanced Chipset Features

    25. Integrated Peripherals

    26. Power Management Setup

    27. Plug and Play Configurations All these screens tend to overwhelm new techs. When they first encounter the many options, some techs feel they need to understand every option on every screen in order to configure CMOS properly. Relax every new motherboard comes with settings that befuddle even the most experienced techs! If we dont talk about a particular CMOS setting somewhere in this book, its probably not important, either to the A+ Certification exams or to a real tech. All these screens tend to overwhelm new techs. When they first encounter the many options, some techs feel they need to understand every option on every screen in order to configure CMOS properly. Relax every new motherboard comes with settings that befuddle even the most experienced techs! If we dont talk about a particular CMOS setting somewhere in this book, its probably not important, either to the A+ Certification exams or to a real tech.

    28. CMOS Password

    29. Phoenix BIOS Setup

    30. Older Award CMOS Setup Discussion Point CMOS Options A typical CMOS setup has tons of options to adjust for. Few techs, if any, know what they all mean. Basically, if it is not covered in the text, it is probably not very critical to the PC function, and it probably is not on the CompTIA A+ exam. Leaving those settings at their default values will usually be fine.Discussion Point CMOS Options A typical CMOS setup has tons of options to adjust for. Few techs, if any, know what they all mean. Basically, if it is not covered in the text, it is probably not very critical to the PC function, and it probably is not on the CompTIA A+ exam. Leaving those settings at their default values will usually be fine.

    31. CMOS Maintenance Common causes of loosing CMOS data are Battery run out, dirt, faulty power supply, electrical surges, and chip creeps The CMOS settings can be checked by memorizing settings, using Optimized defaults, and backing up a copy of the CMOS Discussion Point Voice of Experience When a CMOS battery dies, get it off the motherboard even if it is soldered in place. An old battery can, and does, leak. If this happens and it goes undetected, the leak will eat into the motherboard and its layers of tracings. Once this happens, you will have to replace the motherboard as it then cannot be repaired.Discussion Point Voice of Experience When a CMOS battery dies, get it off the motherboard even if it is soldered in place. An old battery can, and does, leak. If this happens and it goes undetected, the leak will eat into the motherboard and its layers of tracings. Once this happens, you will have to replace the motherboard as it then cannot be repaired.

    32. Battery Since the data stored on a CMOS chip can be saved, power is required when the computer is turned off Power is supplied by a battery on the motherboard Batteries are mounted in one of three ways: External battery (now obsolete) Onboard battery Built-in battery (built into the CMOS chip and very common today)

    33. Clues to a Weak Battery Clock in Windows begins to slow down System keeps losing CMOS data when you turn it off If you have an external battery, check it with a voltmeter (3.6 or 6 volts) If a built-in battery dies, replace the motherboard (seldom happens)

    34. Flash ROM Flash ROM is a new type of ROM chip developed by Intel Can be reprogrammed without the chip being removed Running a small command line program combined with an update file can change or update the BIOS In reality, CMOS no longer exists because flash ROMs (and now Non-Volatile RAM or NVRAM) now hold the system BIOS and CMOS settings but the term is still used The battery only keeps the clock running nowadays Discussion Point Modern CMOS In the newer version of motherboards, the CMOS chip has almost been phased out. Since the advent of the Flash ROM, the programmable ROM chip now has the ability to store the CMOS data within itself, eliminating the need for a separate CMOS chip. Tech Tip Programmable ROM Variants Most techs use one of three termsEPROM, EEPROM, or Flash ROMas the generic catchall term for end user-programmable ROM chips, regardless of the fact that each represents a distinct technology for rewriting the System BIOS. Knowing the differences wont buy you a cup of coffee, but here goes anyway. Erasable Programmable Read-Only Memory (EPROM) chips were an early variant on Flash ROM. You could erase their data by exposing them to ultraviolet light using a special machine. An iridescent sticker on the top of the chip prevented accidental UV exposure. To upgrade the System BIOS on an EPROM chip, you had to send the entire motherboard to the manufacturer. Not very convenient! The Electrically Erasable Programmable ROM (EEPROM) chip is a better solution. EEPROMs work basically like EPROMs, but instead of using UV, you only need electricity to rewrite their contents. To change the contents of an EEPROM chip, you simply boot to a floppy and run a simple program provided by the BIOS manufacturer. Flash ROM chips are functionally equivalent to EEPROM chips, but the Flash ROM technology is faster at rewriting the chip. Most motherboards produced today use Flash ROM. Discussion Point Modern CMOS In the newer version of motherboards, the CMOS chip has almost been phased out. Since the advent of the Flash ROM, the programmable ROM chip now has the ability to store the CMOS data within itself, eliminating the need for a separate CMOS chip. Tech Tip Programmable ROM Variants Most techs use one of three termsEPROM, EEPROM, or Flash ROMas the generic catchall term for end user-programmable ROM chips, regardless of the fact that each represents a distinct technology for rewriting the System BIOS. Knowing the differences wont buy you a cup of coffee, but here goes anyway. Erasable Programmable Read-Only Memory (EPROM) chips were an early variant on Flash ROM. You could erase their data by exposing them to ultraviolet light using a special machine. An iridescent sticker on the top of the chip prevented accidental UV exposure. To upgrade the System BIOS on an EPROM chip, you had to send the entire motherboard to the manufacturer. Not very convenient! The Electrically Erasable Programmable ROM (EEPROM) chip is a better solution. EEPROMs work basically like EPROMs, but instead of using UV, you only need electricity to rewrite their contents. To change the contents of an EEPROM chip, you simply boot to a floppy and run a simple program provided by the BIOS manufacturer. Flash ROM chips are functionally equivalent to EEPROM chips, but the Flash ROM technology is faster at rewriting the chip. Most motherboards produced today use Flash ROM.

    35. BIOS and Device Drivers

    36. BYOB Because computer makers could not predict all the new types of hardware that may come out, ways to bring your own BIOS (BYOB) were invented: Option ROM is a BIOS chip embedded on the adapter card itself every video card today comes with its own BIOS Most new hardware devices use device drivers to tell the BIOS how to talk to the CPU Most devices with onboard BIOS use it only for internal needs (internal function) and use a device driver to talk to the CPU

    37. Device Drivers A device driver is a file that contains the BIOS commands necessary to communicate with the devices they support Loaded in to the RAM when the system boots All devices come with their own device drivers Device drivers have one big limitationthey dont start until the operating system starts them. Some devices still use ROM BIOS to enable them to boot the system. Device drivers have one big limitationthey dont start until the operating system starts them. Some devices still use ROM BIOS to enable them to boot the system.

    38. Where are the Device Drivers? Registry Binary file that contains the configuration settings and device driver information Control Panel Applets that enable the configuration of a broad range of system devices Device Manager Used for changing or removing drivers for any particular device REGEDIT and REGEDIT32 Enables you to access and update the Registry directly

    39. CONFIG.SYS CONFIG.SYS is a special file through which DOS loads the device drivers Located in the root directory of the C: drive The EDIT/SYSEDIT program is used for editing such files Used to load extra BIOS for hardware that is not supported by the system BIOS Windows NT, 2000, and XP also support CONFIG.SYS, but they do it in a very different way. Windows NT, 2000, and XP also support CONFIG.SYS, but they do it in a very different way.

    40. SYSTEM.INI The SYSTEM.INI file is located in the \Windows directory Broken up into groups and each group is identified by the name in square brackets that starts the section Standard sections are [boot], [keyboard], [boot description], [386Enh], and [drives] Most drivers that load are located in the [386 Enh] section

    41. SYSTEM.INI

    42. SYSEDIT

    43. Control Panel

    44. Device Manager Windows NT 4 does not have a Device Manager. To install device drivers in Windows NT, you just use the various icons in the Control Panel. Windows NT 4 does not have a Device Manager. To install device drivers in Windows NT, you just use the various icons in the Control Panel.

    45. Editing the Registry Discussion Point Editing the Registry Extreme caution must be used when manually editing the registry file via REGEDIT or REGEDT32. Once you make changes in the registry, the changes are saved immediately. There is no manual Save or Undo command to reverse any changes made. Changes take effect upon rebooting. If the changes made render the registry unusable, Windows will not boot. Discussion Point Editing the Registry Extreme caution must be used when manually editing the registry file via REGEDIT or REGEDT32. Once you make changes in the registry, the changes are saved immediately. There is no manual Save or Undo command to reverse any changes made. Changes take effect upon rebooting. If the changes made render the registry unusable, Windows will not boot.

    46. Power-On Self Test (POST)

    47. Power-On Self Test (POST) The Power-On Self Test (POST) is a special program stored on the ROM chip Initiated when the computer is turned on, or is reset Checks out the system every time the computer boots

    48. Beep Codes When the computer is booted it first tests the most basic parts It generates a series of beeps if anything is wrong Computers with a bad power supply generate intermittent beep codes Turn the computer on and off several times if you get different beep codes, then its probably the power supply Discussion Point Beep Codes and POST Codes Each BIOS manufacturer sets the beep codes to their 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. Most systems now use beeps to warn you that the system is overheating. These beeps dont take place at bootthey happen after the system has run for a few minutes. An overheated system is a serious problem, so dont confuse it with a beep error code! Discussion Point Beep Codes and POST Codes Each BIOS manufacturer sets the beep codes to their 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. Most systems now use beeps to warn you that the system is overheating. These beeps dont take place at bootthey happen after the system has run for a few minutes. An overheated system is a serious problem, so dont confuse it with a beep error code!

    49. AMI Beep Codes

    50. Phoenix Beep Codes Where do I find the meaning of the beeps? AMI BIOS: www.ami.com/support/doclib.cfm Phoenix BIOS: www.phoenix.com/pcuser/BIOS/phoenix_home.htm Award BIOS: www.phoenix.com/pcuser/BIOS/award_error_codes.htm (Award merged with Phoenix a few years ago.) Where do I find the meaning of the beeps? AMI BIOS: www.ami.com/support/doclib.cfm Phoenix BIOS: www.phoenix.com/pcuser/BIOS/phoenix_home.htm Award BIOS: www.phoenix.com/pcuser/BIOS/award_error_codes.htm (Award merged with Phoenix a few years ago.)

    51. Common Errors Exercise Beep Codes and POST Codes Set up some errors designed to generate beep codes from the BIOS. Remove the RAM and the display adapter. If you have a POST card available, disable a motherboard, or use a dead motherboard to demonstrate how a POST card displays errors.Exercise Beep Codes and POST Codes Set up some errors designed to generate beep codes from the BIOS. Remove the RAM and the display adapter. If you have a POST card available, disable a motherboard, or use a dead motherboard to demonstrate how a POST card displays errors.

    52. Error Messages If anything other than the most basic parts does not pass the POST, then a text message will appear on the screen: Numeric error codes Text error codes

    53. Text-Based Error Message

    54. POST Cards POST cards are devices that monitor POSTs and report on the hardware that may be causing problems Turn the PC off, plug in the card, and reboot POST error codes do not fix the computer they just tell you where to look If all else fails, replace the motherboard

    55. The Boot Process The CPU is the first component that gets initialized when the computer is turned on It reads a special wire called power good once the power supply provides the proper voltage to the CPU Every CPU has a built-in memory address with the first line of the POST program on the system ROM

    56. The Boot Process The last BIOS function called by POST is the bootstrap loader The bootstrap loader loads the operating system either from the floppy or the hard drive The bootstrap loader generates an error if it cannot find the bootable disk

    57. Non-System Disk Error

    58. The Boot Process Boot configuration: The CMOS setting enables you to change the order in which the boot loader will search the devices for the operating system The boot order is changed to prevent hackers from inserting a bootable floppy and accessing the system 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. Exercise CMOS Settings With a functional computer, demonstrate making changes to the CMOS, then have the students make some changes to the CMOS. Try disabling and enabling the cache to demonstrate the speed difference. Go through the CMOS pages and make different changes to demonstrate the effects on the computer. Also, be sure to show how to disable the floppy boot, and how to configure the hard drive geometry.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. Exercise CMOS Settings With a functional computer, demonstrate making changes to the CMOS, then have the students make some changes to the CMOS. Try disabling and enabling the cache to demonstrate the speed difference. Go through the CMOS pages and make different changes to demonstrate the effects on the computer. Also, be sure to show how to disable the floppy boot, and how to configure the hard drive geometry.

    59. Changing the Boot Order Many BIOS programs have CMOS settings that allow you to change the order in which the boot loader searches for an operating system