微机组成原理2

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Tools used by hardware or software to communicate with the other:
Memory addresses I/O addresses Interrupt request numbers (IRQs) Direct memory access (DMA) channels
Involves initially turning on power with on/off switch More stressful than soft boot because of initial power surge through equipment Uses OS to reboot Faster than hard boot
Boot Step 1 Parts of the Boot Process
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Step 1: POST Step 2: ROM BIOS startup program searches for and loads an OS Step 3: OS configures the system and completes its own loading Step 4: User executes application software

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Communicates with hardware using system resources; uses BIOS or device drivers for interface to system resources
Categories of PC Software
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BIOS (basic input/output system) and device drivers Operating system (OS) Application software

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All four types depend on certain lines on a bus on the motherboard
System Resources
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The 8-bit and 16-bit ISA Slots
8-bit ISA bus had a limited number of system resources available to it Number was increased with invention of 16-bit ISA bus
Interrupt Request Number (IRQ)
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Line on a bus that a device uses to alert the CPU that it needs servicing

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Common Uses for Some IRQs
Interruptions to CPU are called hardware interrupts
How Memory Addresses Are Assigned
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Shadowing ROM
Process of copying programs from ROM to RAM for execution
I/O Addresses
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Numbers the CPU can use to access hardware devices, in same way it uses memory addresses to access physical memory Also called port addresses or ports

One for DMA controller to request clearance from CPU One used by CPU to acknowledge that DMA controller is free to send data over data lines without interference from CPU

Consists of programs that instruct computers to perform specific tasks
Operating System (OS)
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Software that controls a computer
Manages hardware Runs applications Provides user interface Stores, retrieves, and manipulates files
How BIOS Finds/Loads the OS
Assignments for I/O Addresses DMA Channels
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Provide shortcuts for a device to send data directly to memory; bypasses CPU A chip on the motherboard contains DMA logic and manages the process Each channel requires two lines to manage it
Hardware and Software Interaction: An Overview
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Software

Intelligence of the computer
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Determines what hardware is present Decides how hardware is configured and used Uses hardware to perform tasks
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continued…
Functions Performed During the Boot
4. Startup BIOS finds the OS, which is loaded, configured, and executed 5. Hardware devices are matched up with the BIOS and device drivers that control them 6. Some application software may be loaded and executed
BIOS and Device Drivers
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Categories of BIOS (firmware) programs

System BIOS Startup BIOS CMOS setup Small programs stored on hard drive that tell computer how to communicate with an input/output device Necessary for communication between OS and more complex devices
Learn … You Will Learn… Chapter 2
How Hardware and Software Work Together
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How hardware and software interact How BIOS and device drivers are used to send instructions to hardware How different operating systems work The steps involved in booting your computer
Startup BIOS Controls the Beginning of the Boot
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Startup BOS is in control for first three steps and beginning of the fourth, where control is turned over to the OS

IRQs
Memory Addresses
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Hexadecimal numbers, often written in segment/offset form, assigned to RAM and ROM so that the CPU can access both
How Memory Addresses Are Assigned
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CPU has fixed number of memory addresses, determined by CPU and bus it is using They can be assigned to any type of physical memory in the system that needs to be addressed by the CPU Once addresses have been assigned (usually during boot process), CPU sees physical memory as a single list that can be accessed using memory addresses
Polling is an alternative to an interrupt
IRQs
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Preconfigured assignments make it easier to configure devices and avoid conflicts with other devices
COM1 and COM2 (for serial devices such as modems) LPT1 and LPT2 (for parallel devices such as printers)
DMA Channels
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Booting up Your Computer
Refers to the computer bringing itself up to an operable state without user intervention Hard boot (cold boot)

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Device drivers

Operating System (OS)
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Works with system BIOS and device drivers to provide instructions to hardware to perform tasks
System Resources
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Soft boot (warm boot)

Plug and Play (PnP) Standard
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Makes installing hardware devices less complicated Rather than having to reset DIP switches and jumpers, OS and/or startup BIOS automatically configures hardware devices to reduce or eliminate conflicting requests for system resources Applies to OS, BIOS on the motherboard, and BIOS on devices
Functions Performed During the Boot
1. Startup BIOS tests essential hardware components (power-on self test or POST) 2. Setup information is used to configure both hardware and software 3. Hardware components are assigned system resources they will later use for communication