computer system
DESCRIPTION
As a part of the course CSC-103,Computer fundamentalsTRANSCRIPT
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The procedure that transforms raw data into useful
information is called processing. This function is divided
between the computer's processor and memory.
The CPU - The processor is also called the central processing
unit (CPU). It manages all devices and performs the actual
processing of data.
The CPU consists of one or more chips attached to the
computer's main circuit board (the motherboard).
Memory - Memory also consists of chips attached to the
motherboard. Memory holds data and program instructions
as the CPU works with them. This memory is called Random
Access Memory (RAM). The CPU can find any piece of data
in RAM, when it needs it for processing.
Processing
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The smallest usable unit of measure for memory is the byte – the
amount of memory required to hold one character, like the letter
A or the numeral 2. Computers work with larger chunks of data,
measured in multiple bytes, as shown below:
Processing
Unit Approx. Value Actual Value (bytes) (bytes) (bytes)
Kilobyte (KB) 1,000 B 1,024
Megabyte (MB) 1,000 KB 1,048,576
Gigabyte (GB) 1,000 MB 1,073,741,824
Terabyte (TB) 1,000 GB 1,099,511,627,776
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How Computer Processes Data
The Control Unit (CU)
The Arithmetic Logic Unit (ALU)CPU
Memory Volatile
Nonvolatile
Flush
Cache
Bus
Registers
Address Bus
Data Bus
Control Bus
Devices that
affect
Processing
Speed
Devices that
affect
Processing
Speed
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How Computer Processes Data
The Control Unit (CU):
All the computer’s resources are managed from the control unit.
This is the logical hub of the computer.
The Arithmetic Logic Unit (ALU):
Arithmetic operations include addition, subtraction, multiplication
and division. When the control unit encounters an instruction that
involves arithmetic or logic, it passes that instruction to ALU.
CPU
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How Computer Processes Data
CPU needs to have millions of memory spaces to quickly read or write
programs and data while they are being used.
Non- Volatile:
Non-volatile chips hold data even when the computer is unplugged.
For example, ROM, PROM(Programmable Read Only Memory),
BIOS.
Volatile:Volatile memory requires power to store data. For example, RAM, SIMM,
DIMM, SO-DIMM.
Flush:Flush memory is a special type of non-volatile memory. It is often used as
portable storage device. Example, Digital camera, portable MP3 player, USB
device. On this devices data is stored using physical switches.
Memory
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How Computer Processes Data
Memory
CPU needs to have millions of memory spaces to quickly read or write
programs and data while they are being used.
Cache:
Moving data between RAM and the CPU’s register is one of the
most time consuming task, as Ram is more slower than CPU. A
partial solution is to add a small memory with the CPU. It is similar
to RAM, but very fast. It holds common or recently used data
Speeds up computer processing. Most computers have several
caches.
When a program is running and CPU needs to read data, it first
checks whether the data is in the Cache memory. If the data is not
there, then CPU loads the data from RAM to registers and also,
loads a copy to the Cache.
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This type of devices is used to tell the processor what must be done based on
the instructions in the memory written by users.
So if, for example, some bytes are found in the memory that corresponds to an
addition instruction the decoder will read them and knows that it is addition
based on the bytes contained then it will activate the control lines to inform the
processor that it is an addition.
Thus the decoder is considered an interface between the memory and the
processor
How Computer Processes Data
Decoders
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How Computer Processes Data
The size of a register, which is sometimes called the word-size indicates the
amount of data or bits with which a processor can work at a single time. The
bigger the word size, the more quickly computer can process data.
In real life the terminologies “16-bit processor” or, “64-bit processor” is refers
to the size of registers in the processor. If other factors are kept normal, than
32-bit registers can process data twice as fast as the registers with 16-bits.
Registers
BUS is the electronic pathway between CPU components. Bus width is
measured in bits. Expansion bus connects to peripherals. System bus
connects CPU and RAM.
BUS
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How Computer Processes Data
System Bus is of three types- Address bus, Data bus, Control bus.
BUS
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How Computer Processes Data
While processing, Address bus and Data bus are used to sharing data
between RAM and CPU.
BUS
System Bus is of three types- Address bus, Data bus, Control bus.
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How Computer Processes Data
System Bus is of three types- Address bus, Data bus, Control bus.
Address - the components pass memory addresses to one another over the address bus.
Control - used to send out signals to coordinate and manage the activities of the motherboard components.
Data - transferred between peripherals, memory and the CPU. Obviously, the data bus can be a very busy pathway.
BUS
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How Computer Processes DataBUS
External Bus Standards-
– Industry Standard Architecture (ISA) : is a 16-bit data bus. Used to
connect modem and other slow devices.
– Local bus : is an internal system bus, that runs between components of
the motherboard.
– Peripheral control interface : ISA in present computer is being replaced
by PCI bus. PCI bus is designed by Intel to make it easier to integrate
new data types : audio, video, graphics, modems and sound cards.
– Accelerated graphics port (AGP): special architecture that enables
video cards to access system’s Ram directly. AGP improves graphics
quality. At present it is enhanced with 3D technology. Extremely fast
bus
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– Universal serial Bus: Connects external devices. Hot swappable.
Allows up to 127 devices. Cameras, printers, and scanners
– IEEE 1394 (FireWire) : Mostly found in MACINTOSH computers and
used to integrate video devices, such as cameras and video cameras.
Many digital TV cameras also use FireWire.
– PC Card: Used exclusively in laptops. Most common use of PC cards
include Wi-Fi cards, network card, thumb scanner (for security) etc.
How Computer Processes DataBUS
External Bus Standards-
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How Computer Processes DataBUS
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Machine Cycle
Fetching
Decoding
Execution
Storing
CPU performance is dependent upon Instruction Count, CPI (Cycles per
instruction) and Clock cycle time. And all three are affected by the instruction
set architecture.
Machine Cycle
Steps by CPU to process data.
Fetching: This is the instruction
cycle. Here, CPU fetches the
instruction from memory to
registers.
Decoding: CPU breaks downs
the instructions to correspond
with the CPU’s instruction set.
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Machine Cycle
Execution: CPU carries out the instructions in order.
Storing: Often CPU may required to store the outcome into the memory.
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How Computer Processes DataProcessors
A processor is a type of microchip that is used to receive, process, and
send out instructions and commands. it is typically made of silicon and
other materials. Processors features are-
Speed of processor
Size of cache
Number of registers
Bit size
Speed of Front side bus
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How Computer Processes DataProcessors
CISC Processor (Complex Instruction Set Computing)
Supplies a large number of complex instructions at the assembly language
level.
During the early years, memory was slow and expensive and the
programming was done in assembly language. Since memory was slow and
instructions could by retrieved up to 10 times faster from a local ROM than
from main memory, programmers tried to put as many instructions as possible
in a microcode.
The CISC approach attempts to minimize the number of instructions per
program, sacrificing the number of cycles per instruction.
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RISC processors (Reduced Instruction Set Computing)
RISC does the opposite, reducing the cycles per instruction at the cost of
the number of instructions per program. It is a type of microprocessor that
has a relatively limited number of instructions.
It is designed to perform a smaller number of types of computer
instructions so that it can operate at a higher speed (perform more million
instructions per second, or millions of instructions per second).
Earlier, computers used only 20% of the instructions. Making the other
80% unnecessary. One advantage of reduced instruction set computers is
that they can execute their instructions very fast because the instructions
are so simple.
How Computer Processes DataProcessors
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Standard computer ports
Keyboard and mouse ports
USB ports
Parallel
Network
Modem
Audio
Serial
Video
Extending The Processors Power
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Serial and parallel ports
Connect to printers or modems
Parallel ports move bits simultaneously
• Made of 8 – 32 wires
• Internal busses are parallel
Serial ports move one bit
• Lower data flow than parallel
• Requires control wires
• UART converts from serial to parallel
Extending The Processors Power
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Serial Communications
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Parallel Communications
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Thank You!
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