CHAPTER 6 Motherboard and ROM BIOS

Chapter Overview Computer Cases Motherboards ROM BIOS

Case holds all the primary electronics of the PC and all the drives. It offers access to the outside world via ports and connectors. The case helps contain electromagnetic interference (EMI). It protects surrounding devices such as TV. The Computer Case

The Computer Case Cont. When considering the case, there are four general rules to keep in mind: Larger cases usually have more expansion capability and are easier to work with. Smaller cases usually have less expansion potential and support fewer internal devices. Cases with more features cost more. You should never run a computer with an open case.

Electromagnetic Interference (EMI). It is a newer form of radio frequency interference (RFI) EMI is the radio frequency that is emitted from an electronic device that is harmful to the surrounding equipment Running a computer without its cover is a sure way to generate EMI

Working with Cases DesktopTower

The Motherboard It defines the computer’s limits of speed, memory and expandability. Is the large circuit board found inside the computer case.

things that you should keep in mind before changing any m/b ! Should be generic to fit into your PC Be sure to verify that it is compatible to your case and power supply Be sure to verify that it is compatible to RAM and Expansion cards Replace rather than repair a damaged motherboard. Before replacing a motherboard, double-check all other components to verify that the motherboard is the problem.

Chip Sets The chip set helps the CPU manage and control the computer. The CPU must be compatible with the chip set. Specialized chips control cache memory and high-speed buses. Different chip sets have different on-board components. On-board components might have fewer features than do expansion card versions.

Basic chip set consist of: Bus controller. Memory controller. Data and address buffer. Peripheral controller.

ROM BIOS Chips Read-only memory (ROM) chips store basic input/output system (BIOS) data—even when the computer power is off. This is necessary so that the system can access the data it needs to start up. The BIOS ( basic input output system) is a software in the form of programs stored on ROM chip. The system BIOS is a ROM chip on the MB used by the computer during the startup (boot process) to check out the system and prepare to run the hardware. Old computers with ROM chip Flash Rom or flash BIOS can update by software.

Classes of BIOS chips include: Core chips: these chips commonly used for the keyboard, parallel and serial ports and speakers, each ROM chip contains between 16 and 64 KB of programming. Updateable chips: several devices on a computer often contain their own flash BIOS or Updatable ROMs including SCSI Controller and video cards. Information stored on a special chip Called complementary metal-oxide semiconductor (CMOS) chips. CMOS chip can store about 64 KB.

Information Stored in the CMOS Floppy disk and hard disk drive types CPU type and speed Random access memory (RAM) size Date and time Serial and parallel port information Plug and Play information Power-saving settings

BIOS and CMOS What's the difference between BIOS and CMOS? Many people use the terms BIOS (basic input/output system) and CMOS (complementary metal oxide semiconductor) to refer to the same thing. Though they are related, they are distinct and separate components of a computer. The BIOS is the program that starts a computer up, and the CMOS is where the BIOS stores the date, time, and system configuration details it needs to start the computer.BIOSCMOS

Cont The BIOS is a small program that controls the computer from the time it powers on until the time the operating system takes over. The BIOS is firmware, which means it cannot store variable data. firmware CMOS is a type of memory technology, but most people use the term to refer to the chip that stores variable data for startup. A computer's BIOS will initialize and control components like the floppy and hard drive controllers and the computer's hardware clock, but the specific parameters for startup and initializing components are stored in the CMOS.memory

Updating CMOS

Determining the BIOS Manufacturer Watch the monitor when the computer boots. Check the computer or motherboard manual. Remove the computer cover and look at the chip. Use a third-party utility program. Cause an error that will launch the setup program.

The Most Common Ways to Access BIOS Setup Programs AMI: Press Delete when the machine begins to boot. Phoenix: Press Ctrl+Alt+Esc, Delete, or F2 when requested. Award: Follow the procedure for AMI or Phoenix.

Main BIOS Screen

Setup Screen for Hard Disk Drive

Advanced Tab

Security Tab

Power Tab

Maintaining CMOS Losing CMOS information is a common problem, some of the more common reasons that CMOS data is lost include the following: The on-board battery has run out. Cards have been removed or inserted in a way that releases electronics discharge (ESD). Improper handling of the motherboard has caused electrical short circuits. Something has been dropped on the M/B. The power supply is Faulty. There have been electrical surges.

Errors indicate lost or corrupt CMOS data: CMOS configuration mismatch. No boot device available CMOS battery state low ( The system is giving you a warning that the battery is getting low on power. Recommendation:  Double-check the battery connection to the motherboard. If the battery is removable, remove and reinsert it.  Replace the CMOS battery, if this is possible with your motherboard.CMOS battery  Troubleshoot the motherboard. Troubleshoot the motherboard Can not locate HD or FDD.

Cont. You should write down CMOS setup information or back it up. There are many third-party CMOS save and restore utility programs available. H/W Plug and Play devices include their own BIOS information.

The CMOS Battery The CMOS chip requires a small trickle voltage from a battery to keep its memory a live. The voltages of CMOS batteries ranges from 3 to 6 volts. Look for battery requirements on the motherboard or in the documentation. The 3 volt lithium watch battery is becoming very popular with M/B suppliers. Expect 2–7 years of battery life, depending on the type of battery. Watch for battery failure indicators. Replace the battery if a computer loses stored CMOS information more than once in a week.

All Other Chips Add-on boards may have ROM chips with their own BIOS data. Display adapters, NIC and sound cards have their own on –board ROM chip Device drivers could be required to provide BIOS support for hardware. A device driver is a program that acts as an interface between the O.S and the control circuits that operate the device. Every time the computer is booted up the CONFIG.SYS file is read and the device drivers are loaded from the hard disk into RAM.

Power-On Self Test The power-on self test (POST) checks every primary device at startup. Beep codes indicate problems before and during the video test. Errors displayed on the screen typically indicate problems after the video test. Errors can be fatal or nonfatal. Fatal errors will halt the system without attempting to load the operating system. memory, disk and display adapter). Non fatal error like missing flopy disk drive. Will still result in the system attempting to load the O.S. Please check page 113 and 114

Chapter Summary You should select a computer case for ease of use and expandability. EMI can harm surrounding equipment. Motherboards use different chip sets with differing capabilities. ROM BIOS chips can be static or updateable. A CMOS program accesses BIOS information stored in CMOS chips. If you change hardware, you must update the CMOS to reflect changes. A CMOS battery ensures that CMOS information is saved.

QUIZ 2 Sunday 6/4/2008 (LAB time). materials: Chapters 5 and 6.