1. Suppose a graduate enters the industry and is asked to select the most cost-effective
computer for use throughout a large organization. An understanding of the
implications of spending more for various alternatives, such as a larger cache
or a higher processor clock rate, is essential to making the decision.
2. Many processors are not used in PCs or servers but in embedded systems.
A designer may program a processor in C that is embedded in some real-time or larger
system, such as an intelligent automobile electronics controller. Debugging the
system may require the use of a logic analyzer that displays the relationship between
interrupt requests from engine sensors and machine-level code.
3. Concepts used in computer architecture find application in other courses.
In particular, the way in which the computer provides architectural support for
programming languages and operating system facilities reinforces concepts from
those areas
ORGANIZATION AND ARCHITECTURE
Computer architecture refers to those attributes of a system
visible to a programmer or, put another way, those attributes that have a
direct impact on the logical execution of a program.
Computer organization refers to the operational units and their
interconnections that realize the architectural specifications.
Examples of architectural attributes include
the instruction set, the number of bits used to represent various data types
(e.g., numbers, characters), I/O mechanisms, and techniques for addressing
memory. Organizational attributes include those hardware details transparent to
the programmer, such as control signals; interfaces between the computer and
peripherals; and the memory technology used.
STRUCTURE AND FUNCTION
A hierarchical
system is a set of interrelated subsystems, each of the latter, in turn,
hierarchical in structure until we reach some lowest level of elementary
subsystem.
• Structure: The way in which the
components are interrelated
• Function: The operation of each
individual component as part of the structure
Function
Both the structure and functioning of a
computer are, in essence, simple. Figure 1.1
depicts the basic functions that a computer
can perform. In general terms, there are
only four:
1.
Data
processing
2.
Data
storage
3.
Data
movement
4.
Control
The computer, of course, must be able to process
data.The data may take a wide variety of forms, and the range of processing
requirements is broad.
It is also essential that a computer store
data. Even if the computer is processing data on the fly (i.e., data come
in and get processed, and the results go out immediately), the computer must
temporarily store at least those pieces of data that are being worked on at any
given moment.Thus, there is at least a short-term data storage function.
Equally important, the computer performs a long-term data storage function. Files
of data are stored on the computer for subsequent retrieval and update.
The computer must be able to move data between
itself and the outside world. The computer’s operating environment consists of
devices that serve as either sources or destinations of data.When data are
received from or delivered to a device that is directly connected to the computer,
the process is known as input–output
(I/O), and the device is referred to as a peripheral.When data are moved over longer distances, to or
from a remote device, the process is known as data communications.
Finally, there must be control of
these three functions. Ultimately, this control
is exercised by the individual(s) who
provides the computer with instructions.Within
the computer, a control unit manages the
computer’s resources and the
performance of its functional parts in response
to those instructions.
The number of possible operations that can be
performed is few. Figure 1.2 depicts the four possible types of operations.
(Figure
1.2a), The computer can
function as a data movement device simply transferring data from one peripheral
or communications line to another.
(Figure
1.2b), It can also function as a data storage device
with data transferred from the external environment to computer storage (read)
and vice versa (write).
(Figure
1.2c) , Show operations
involving data processing.
(Figure
1.2d), on data either in
storage or en route between storage and the external environment .
Structure
Figure 1.3 is the simplest possible
depiction of a computer. The computer interacts in some fashion with its
external environment. In general, all of its linkages to the external
environment can be classified as peripheral devices or communication lines.We
will have something to say about both types of linkages.
There are four main structural components:
• Central processing unit (CPU): Controls
the operation of the computer and performs its data processing functions; often
simply referred to as processor.
• Main memory: Stores data.
• I/O: Moves data between the
computer and its external environment.
• System interconnection: Some
mechanism that provides for communication among CPU, main memory, and I/O. A
common example of system interconnection is by means of a system bus,
consisting of a number of conducting wires to which all the other components
attach.
There may be one or more of each of the
aforementioned components. Traditionally, there has been just a single
processor. In recent years, there has been increasing use of multiple
processors in a single computer.
The most interesting and in some ways the most
complex component is the CPU. Its major structural components are as follows:
• Control unit: Controls the
operation of the CPU and hence the computer
• Arithmetic and logic unit (ALU): Performs
the computer’s data processing functions
• Registers: Provides storage
internal to the CPU
• CPU interconnection: Some mechanism
that provides for communication among the control unit, ALU, and registers
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