Computer System Architecture (MCA-301)
Ravinder Kamboj
Asst. Professor
LCET, Katani Kalan
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 Digital computer
 What is Computer System?
 Computer Organization v/s Computer
Architecture
 Computer Architecture
 Types of computer architecture
◦ Von Neumann Architecture
◦ Harvard Architecture
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 A computer that stores data in terms of digits
(numbers) and proceeds in discrete steps
from one state to the next.
 The states of a digital computer typically
involve binary digits which may take the form
of the presence or absence of magnetic
markers in a storage medium, on-off
switches. In digital computers, even
letters, words and whole texts are
represented digitally.
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 If you are not concerned with the internal
mechanism of a digital computer, you can simply
denote it as a black box.
 However, you still need to denote the tasks finished
by a digital computer for distinguishing it from other
types of black boxes.
 computational model of a digital computer is
proposed.
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RAM
Central
Processing
Unit (CPU)
Input Input-Output Output
Device Processor Device
(IOP)
Figure: 1.1.2 Block diagram of digital computer
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 A computer system is sometimes subdivided
into functional entities:
◦ Hardware and Software
 Hardware of the computer consists of al the
electronic components ( Physical entity of
devices)
 Hardware is divided into three major parts
(CPU, Memory and I/O devices)
 Computer software consists of the instruction
and data that computer manipulates to
perform various tasks.
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 Computer organization is  Computer architecture is
concerned with the structure and
concerned with the way the behavior of the computer as
hardware component seen by user.
 It includes the
together to form the information, formats, the
computer system. instruction set, and techniques
of addressing memory.
 The various components  The architectural design of a
are assumed to be in same computer system is concerned
with the specifications of various
place and the task is to functional modules, such as
investigate the processors and memories, and
structuring them together into a
organizational structure to computer system.
verify that the computer
parts operate as intended.
Computer Organization Computer Architecture
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Applications
Operating
System
Instruction set
Compiler Firmware architecture
Instr. Set Proc. I/O system
Datapath & Control
Machine
Digital Design
organization
Circuit Design
Layout
Many levels of abstraction
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 It is named after the mathematician and
early computer scientist John Von Neumann.
 The computer has single storage
system(memory) for storing data as well as
program to be executed.
 Processor needs two clock cycles to complete an
instruction. Pipelining the instructions is not
possible with this architecture.
 In the first clock cycle the processor gets the
instruction from memory and decodes it. In the
next clock cycle the required data is taken from
memory. For each instruction this cycle repeats
and hence needs two cycles to complete an
instruction.
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 The name is originated from "Harvard Mark I" a
relay based old computer.
 The computer has two separate memories for
storing data and program.
 Processor can complete an instruction in one
cycle if appropriate pipelining strategies are
implemented.
 In the first stage of pipeline the instruction to be
executed can be taken from program memory. In
the second stage of pipeline data is taken from
the data memory using the decoded instruction
or address.
 Double memory bandwidth is required.
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