computer hardware

created by jithesh B nair systems manager people institute of management studies munnad

Computer Hardware and Flow of Information

What is a Computer?

• Computer– Device capable of performing computations and making logical

decisions– Computers process data under the control of sets of instructions

called computer programs

– Personal computers: economical enough for individual– Distributed computing: computing distributed over networks– Client/server computing: sharing of information across computer

networks between file servers and clients (personal computers)

What is a Computer? (cont.)

• Computer Hardware –Various devices comprising a computer: –Keyboard, screen, mouse, disks, memory, CD-ROM, and

processing units

High-levelLanguage

AssemblyLanguage

Firmware

MachineCode

Hardware

User

ApplicationSoftware

OS

What is a Computer? (cont.)

• Computer Software – Computer Programs that run on a computer, including

• Operation System (OS)• Application Software• Computer Language

High-levelLanguage

AssemblyLanguage

Firmware

MachineCode

Hardware

User

ApplicationSoftware

OS

Computer Architecture

A Typical Von-Neumann Architecture

Example:

1. Input unit2. Output unit 3. Memory unit 4. Arithmetic and logic unit (ALU) 5. Central processing unit (CPU) 6. Secondary storage unit

Control Circuit(ex: PC: Program Counter)

ALUMemory I/O

CPU

Computer Architecture (cont.)

Five major operations performed by a computer system:1. Input

• Obtains information from input devices (keyboard, mouse)2. Storage

• Primaryo or main memory or internal memory / memory o the only one directly accessible to the CPU. o The CPU continuously reads instructions stored there and executes them as required. o Eg: ROM (Read Only Memory): CMOS, EPROMo RAM (Random Access Memory): SRAM, DRAM, SIMM, DIMM• Secondaryo known as external memory or auxiliary storage o Not directly accessible by the CPUo Eg: Hard disk, flash memory, floppy disks


Six logical units in every computer (cont):

3. Processing

4. Output• Outputs information (to screen, to printer, to control other devices

5. Control


Basic computer functional units control

• Arithmetic and logic unit (ALU) – part of CPU Performs arithmetic calculations (addition, subtraction...)

and logic decisions• Control unit (CU) - part of CPU

Supervises and coordinates the other sections of the computer


• Central Processing Unit (CPU)– “brain” of a computer, consisting of

• Arithmetic and logic unit (ALU): performs arithmetic calculations (addition, subtraction...) and logic decisions (>, <, =, ...)

• Control Unit (CU): decodes each machine instruction and sends signal to other components for carrying out the instruction.

– An integrated circuit (IC) that is a full central processing unit is called a microprocessor (p); a CPU’s current instruction and data values are stored temporally inside the CPU in special high-speed memory location called registers.

– CPU speed: ? MHz (M: Mega = 106, Hz=1/sec);


• Memory– A large collection of circuits, each capable of storing bit– Cells (words): manageable units; typical size is 8 bits (1 byte),

some machines are 16 bits (2 bytes) and some are 32 bits or 64 bits

• Byte (8 bits), KB (kilobyte, 103 210 bytes), MB (Megabyte, 106 220 bytes), GB (Gigabyte, 109 230 bytes). Note: k ≠ K because 1000 ≠ 1024.


– Computer memory is comparable to a collection of numbered mailboxes. To identify individual cells in a machine’s main memory, each cell is assigned a unique name, called its address

– The organization of byte-size memory cell

...01001000 01100101 01101100 0110111101101100 00101110

H e l l o ,ASCII

...Data

Address 0000 0101 0000 0110 0000 0111 0000 1000 0001 0001 0001 0010

Address BusData Bus

0 0 0 0 0 1 0 1 Low-order endHigh-order end

Least Significant Bit (LSB)Most Significant Bit (MSB)

A Typical Von-Neumann Architecture

Example:

1. Input unit2. Output unit 3. Memory unit 4. Arithmetic and logic unit (ALU) 5. Central processing unit (CPU) 6. Secondary storage unit

Control Circuit(ex: PC: Program Counter)

ALUMemory I/O

CPU

Computer’s Bus System• A bus, in computing, is a set of physical connections (cables,

printed circuits, etc.) which can be shared by multiple hardware components in order to communicate with one another.

• think of a bus as a highway on which data travels within a computer.

Computer’s Bus System (cont..)

• Purpose of buses = to reduce the number of "pathways" needed for communication between the components, by carrying out all communications over a single data channel.

Types of Computer’s Bus

• There are generally two buses within a computer: • Internal bus (system bus)

– Allows the processor to communicate with the system's central memory (the RAM).

• External bus (expansion bus) – Allows various motherboard components (USB, serial, and

parallel ports, cards inserted in PCI connectors, hard drives, CD-ROM and CD-RW drives, etc.) to communicate with one another.

– However, it is mainly used to add new devices using what are called expansion slots connected to the input/output bus.

Types of External Buses• There are five major types of external bus’s found on

the common motherboard.– ISA (Industry Standard Architecture)

• This bus is the low speed work horse of the system.• commonly find a Sound Card hooked up this type BUS.

– PCI (Peripheral Component Interconnect)• Supports 32-64 bit bus and is the reigning standard of

external buses.• Fast • slowly making the ISA fade away. Go with a PCI Bus Card

when possible.

Types of External Buses (cont…)

– AGP (Accelerated Graphics Port)• This Bus provides from 2 to 4 times the speed of the PCI • used for video expansion only.• great way to go and takes a lot of stress off the CPU, thus

gaining in performance all the way around.

– USB (Universal Serial Bus)• allows to hook up to 127 devices. • probably going to wipe out PS/2 ports and more. • Allows to hot swap devices or plug and unplug devices while

system is running. • a great feature and is incorporated on most new

motherboards.

Types of External Buses (cont…)

– IDE (Intelligent Drive Electronics) • used mostly for disk drives • connects up to two devices on one connection. • More than likely hard drive and CD-ROM are connected through

this type bus.

Operation of bus protocol

• PCI

• SCSI

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