Computer Hardware

Processing and Internal Memory

Secondary Storage

Input Output

Processing

InternalMemory

CPU - Central Processing Unit

Parts of the CPU CU - Control Unit ALU - Arithmetic/Logic Unit registers internal bus

Also referred to as the microprocessor

Control Unit

part of the CPU that coordinates the operation of the computer

manages the flow of data converts instructions into

commands that the computer can understand

Arithmetic Logic Unit

Performs the actual processing by performing arithmetic and logic operations on the data

Registers

special high speed storage locations within the CPU instruction register address register storage register accumulator

Memory (RAM)

The section of the computer that holds: data and program instructions

awaiting processing intermediate processing results processed output

Processing All program instructions are converted

to binary instructions called machine language.

The processing of a single machine language instruction is accomplished in a four step machine cycle

The system clock synchronizes the machine cycle measured in Megahertz (MHz) 1 MHz is 1 million clock cycles per second

Machine Cycle

Machine Cycle

Instruction cycle (I-cycle) The control unit fetches from memory the next

command to be executed. The control unit d e c o d e s the command into an

instruction that the ALU can process. CU Execution cycle (E-cycle)

The control unit retrieves the needed data from memory and commands the ALU to e x e c u t e the required instruction

The control unit stores the result in memory.

The System Unit

Memory

types of internal memory RAM - Random Access Memory Cache Memory ROM - Read Only Memory

Random Access Memory (Main Memory) used to store programs and data

on which the computer is currently working

measured in megabytes on PC’s volatile memory SIMM, DIMM DRAM, SDRAM

Cache Memory

A storage area, where the computer stores the most recently accessed data.

external cache internal cache

level 2 cache (L2 cache) SRAM

Read Only Memory

a software-in-hardware module that can be read but not written on

nonvolatile memory important pieces of system

software are stored in ROM

System Bus

Communication system for the computer

a set of wires etched into the system board (motherboard)

Types of System Buses internal bus - on the microprocessor data bus - links the CPU to RAM expansion bus - extends the data bus to

establish links with peripherals ISA, EISA

local bus - handle the most time critical busing operations (display, storage, network) PCI

Copyright (c) 1998 by Harcourt Brace & Company. All rights reserved.

Add in Boards (Cards) Customization of computer card-like pieces of hardware that contain

the circuitry to perform specific functions Variety of brands and functions

graphics adapter fax/modem boardsound card network card

plug into expansion slots

Ports sockets that allow you to plug in external

hardware devices parallel

25 holes printers, tape drives

serial (com ports) 9 or 25 pins connects low speed peripherals such as

scanners and external modems Universal Serial Bus (USB)

mouse port, keyboard port

Increasing Computer Speed increase clock speed increase word size add cache, more RAM packing circuits closer together symmetric multiprocessing RISC architecture pipelining instructions

Pipelining Instructions

PC Microprocessors

8088 and 8086 80286 80386 SX and DX 80486 or i486 SX and DX Intel’s Pentium, Pentium Pro, Pentium II,

Celeron, Pentium III, Pentium III Xeon MMX

Cyrix, AMD DEC Alpha