Transcript Chapter 6
BIOS Chapter 6 CPU Communication with the System • The CPU needs to communicate with all components of the computer system • The Northbridge chip/circuitry controls the high speed communication channels • RAM • Video • The Southbridge chip/circuitry controls the low speed communication channels. Input/Output Controller Hub (ICH) • Keyboard • USB • Disk drives BIOS • Basic Input/Output Services • Contains programs to allow CPU to interact with the system before the operating system is loaded • Stored in ROM • • • • ROM - Read Only Memory PROM - Programmable Read Only Memory EPROM - Erasable Programmable Read Only Memory EEPROM - Electrically Erasable Programmable Read Only Memory • Flash ROM • Firmware CMOS • Complementary Metal-Oxide Semiconductor • Holds data about connected devices to be used by the BIOS programs • Also acts as the clock • Modify CMOS • Every computer has a system setup program that can be accessed at boot time Tour through CMOS Setup Program • MB Intelligent Tweaker • Can change the voltage and multiplier settings for the CPU • Advanced BIOS Features • Covers a variety of settings such as boot devices and order • Virtualization Support • Hardware support for a virtual machine • Chassis Intrusion Detection • Advanced Chipset Features Tour through CMOS Setup Program • Integrated Peripherals • Configure, enable, and disable onboard devices • Power Management Setup • Control how and when devices turn off and on to conserve power • Overclocking • PnP/PCI Configurations • Rarely used • Trusted Platform Module Option ROM and Device Drivers • BIOS programs must be available for all devices attached to the computer system • Option ROM • ROM chip is on the device controller • Device Drivers • Software file • Programs are loaded into RAM Power On Self Test (POST) • The Beep Codes • Text Errors • Occur after video has passed its test • POST Cards • Expansion card used to read and display the POST codes • Useful for “dead” systems The Boot Process • Power supply circuitry test for proper voltage then sends signal down “power good” wire to awaken the CPU • CPU sends a built-in memory address across address bus which is the first line of the POST program in the system ROM • Once the POST program is done, it passes control to the last BIOS function, the bootstrap loader • The bootstrap loader reads the CMOS data to find the OS, bootable drives • If a valid boot program is found in a boot sector, it is run; otherwise the next device is tried • The OS is then loaded • Preboot execution environment (PXE) allows for the retrieval of an OS over a network for booting Care and Feeding of BIOS and CMOS • Losing CMOS Settings • How do you know? • • • • CMOS configuration mismatch CMOS data/time not set No boot device available CMOS battery state low • How did it happen? • • • • • Pulling and inserting cards Touching the motherboard Faulty power supplies Electrical surges Dead battery • Flashing ROM UEFI • Unified Extensible Firmware Interface • Replaces BIOS • UEFI support 32-bit or 64-bit booting • UEFI handles all boot-loading duties • UEFI is not dependent on x86 firmware