Chapter 3 Flashcards
BIOS
The BIOS (basic input/output system) is an important motherboard component that has the following functions:
- Holds and executes POST (power-on self-test)—a program that identifies, tests, and initializes basic hardware components
- Holds a basic routine called a bootstrap program that locates an operating system and allows it to load
- Holds Setup (also called BIOS setup, system Setup, and CMOS setup), which is a program that allows settings to be viewed and managed (Schmidt 94)
POST
POST performs basic tests of individual hardware components, such as the motherboard, RAM modules, keyboard, optical drive, and hard drive. When a computer is turned on with the power switch, BIOS executes POST. An indication that POST is running is that the lights on the keyboard momentarily flash on and then off, or you will see the hard drive or optical drive light momentarily flash. Turning the computer on with the power switch is known as a cold boot. Users perform a cold boot every time they power on their computer. A technician performs a cold boot when he or she is troubleshooting a computer and needs POST to execute. BIOS can be configured to reduce the time and number of devices checked by POST. (Schmidt 94-95)
setup program
Computers have Setup software built into the system BIOS chip on the motherboard that you can access with specific keystrokes determined by the BIOS manufacturer. During the boot process, most computers display a message stating which keystroke(s) will launch the Setup program. The message shown is usually in one of the four screen corners. (Schmidt 95)
flash BIOS
Flash BIOS is the most common type of BIOS; it allows changing the BIOS without installing a new chip or chips. Common computer BIOS manufacturers include AMI (American Megatrends, Inc.), Phoenix, Byosoft (Nanjing Byosoft Co., Ltd), and Insyde Software. Many computer companies produce their own BIOS chips or subcontract with one of these companies to customize the BIOS. (Schmidt 96)
BIOS upgrade
A computer may need a BIOS upgrade for a variety of reasons, including the following:
- To provide support for new or upgraded hardware
- To provide support for a higher-capacity hard drive
- For increased virus protection
- For optional password protection
- To solve problems with the current version (Schmidt 96)
BIOS update preventing measures in case of failure
Some motherboards have a utility that allows recovery if a BIOS becomes corrupted or the BIOS update fails. Another option is a flash BIOS recovery jumper or switch used for BIOS recovery. A third option is a backup BIOS in case a BIOS upgrade fails or stalls during the upgrade process. Also, an alternative is having a portion of the BIOS that cannot be changed so that the computer can still boot, even if a BIOS update fails. If the motherboard manufacturer does not provide one of these alternatives, the motherboard will have to be replaced. A computer without an operational BIOS cannot boot. See the motherboard manual or documentation for specific BIOS details and the method that is being used to protect the BIOS. (Schmidt 96)
UEFI
UEFI (Unified Extensible Firmware Interface, and sometimes seen as simply EFI) is the interface between the operating system and firmware, which could be the traditional BIOS, or UEFI could replace the BIOS. The traditional BIOS has roots in the original PC; the BIOS always checked for certain things such as a keyboard before allowing the system to boot. A traditional BIOS made configuring kiosks and touchscreen technologies difficult. UEFI fixed these issues (Schmidt 96)
Advantages of UEFI BIOS interface
Many manufacturers have moved to the UEFI type of BIOS for the following reasons:
- It is a graphical environment that provides mouse support.
- It enables you to have a virus-scanning utility that is not operating system dependent.
- It offers more BIOS software that is not just configuration screens.
- It offers optional Internet access for troubleshooting or download capabilities.
- It offers better system support for cooling, voltage levels, performance, and security.
- It provides support for increased hard drive capacities. (Schmidt 97)
CMOS
Settings changed in system BIOS are recorded and stored in CMOS (complementary metaloxide semiconductor) found in the motherboard chipset (south bridge or I/O controller hub). CMOS is memory that requires a small amount of power, provided by a small coin-sized lithium battery when the system is powered off. The memory holds the settings configured through BIOS. Part of the BIOS software routine that runs after the computer is turned on checks CMOS for information about what components are supposed to be installed. These components are then tested (Schmidt 100)
other parameters
Other possible parameters contained and set via the Setup program or operating system are IRQs (interrupt requests), I/O (input/output) addresses, DMA (direct memory access) channels, and memory addresses. These parameters are assigned to individual adapters and ports, such as disk controllers, and the USB, serial, parallel, and mouse ports. Sometimes these ports must be disabled through Setup in order for other devices or adapter ports to work. No matter how the parameters are assigned, collectively they are known as system resources. These are not the same system resources that we refer to when we discuss Windows operating systems. Let’s take a look at three important system resources: IRQs, I/O addresses, and memory addresses. (Schmidt 102)
IRQ’s
The processor prioritizes device requests through the use of IRQ. An IRQ (interrupt request) is a number assigned to an expansion adapter or port so orderly communication can occur between the device or port and the processor. For example, when a key is pressed and the mouse is moved simultaneously, the keyboard has the highest priority because of its IRQ number. (Schmidt 102)
APIC
Older computers had 16 interrupts numbered 0 through 15. The chip that controls the interrupts is known as the interrupt controller chip. Today, computers have APICs (advanced programmable interrupt controllers) that support more interrupt outputs (24, for example) and provide more flexibility than a traditional system, which does not normally support more than one device to an interrupt. APICs allow sharing interrupts between devices. There are two common types of APICs: LAPIC (local APIC) and I/O APIC. LAPIC is normally integrated into each CPU and has its own timer, whereas the I/O APIC is used throughout any of the peripheral buses and is integrated into the chipset. The chipsets used today are backward compatible with the traditional interrupts used. (Schmidt 102)
indication of IRQ’s conflicts
Indications of a resource conflict (including IRQ, DMA, I/O address, and memory address conflicts) are as follows:
- The new device is installed and the new device or a device already installed does not work.
- The computer locks up or restarts when performing a specific function, such as when playing or recording audio.
- The computer hangs during startup or shutdown.
- A device does not work properly or fails to work at all. (Schmidt 104)
PCI interrupt
When a PC first boots, the operating system discovers what AGP, PCI, and PCIe adapters and devices are present and what system resources each one needs. The operating system allocates resources such as an interrupt to the adapter/device. If the adapter or device has a ROM or flash BIOS chip installed that contains software that initializes and/or controls the device, the software is allowed to execute during the boot process.
PCI/PCIe devices use interrupts called INTA, INTB, INTC, INTD, and so on. These interrupts are commonly referred to as PCI interrupts. (Schmidt 105)
PCI steering
PCI interrupts can also be mapped to one of the traditional interrupts, usually IRQ 9, 10, 11, and 12. With so many devices installed in today’s computers, this is solved with a technique called IRQ steering. IRQ steering allows multiple adapters to be mapped to the same traditional IRQ. PCI steering (another name for IRQ steering) allows multiple devices to share the same interrupt. Adapters should be able to share the same resources without conflicts. When IRQ steering is enabled and when an adapter needs an interrupt, the operating system finds an available interrupt (which may be currently used by another device that does not need it) and allows the requesting device to use it. (Schmidt 105)
