COURSE: UNDERSTANDING PC AND TROUBLESHOOTING
UNIVERSITY: MANIPAL UNIVERSITY JAIPUR
TOPIC: The CPU
INTRODUCTION: To know the meaning of CPU or the way to troubleshoot it. You must know the physical and
mechanical concepts of PC. PC or personal computer is a small digital device made from Microprocessor chip and
designed especially for the use of individual person. PC is not a single device. It is the combination of different
components and devices. Before we start troubleshooting a PC, we must understand these different devices. In this unit
you will study one of those devices in detail and learn how to troubleshoot. You may feel amused to read the word
troubleshooting without knowing the meaning of it. Troubleshooting is a way of detecting the problem in the PC or the
cause of the problem and fixing the problem so that the PC can function according to the needs of the user. This
problem may be from any of the components of the PC.
Since all these components are interrelated the failure in one device may cause the whole system to stop working or
work haphazardly. Troubleshooting is a technique to solve this problem and make the system work appropriate. The
different components of PC are CPU, motherboard, memory, hard drives, monitor, ports, adapter USB, etc. which you
will be studying one by one in later units. In this unit you will learn how to trouble shoot the CPU, which is an essential
part of a computer. In fact, it functions as a brain to the system. We often consider CPU to be a synonym for cabinet.
However, you should keep in mind that there is a vast difference between the two. The CPU is the controller while the
cabinet is a component that holds CPU and memory along with Buses for data flow. Integrated circuit technology has
realized the importance of the Central Processing Unit (Processor) as it is expected to perform three major functions.
They are mathematical calculations, logical comparisons, and data manipulation.
Though the concept of central processing is not new, it was only after the integration of central processing functions into
a single silicon chip, that it became well known as CPU. In the mid-1970s, this single silicon chip referred to as
microprocessor chip, was instrumental in enhancing the speed and performance of the computer greatly. To become an
effective techie, you should know the essential components of CPU. You should also know the important specifications
of CPU and its features. This unit will not only give you an insight into the evolution of CPU and its capabilities but also
help you to learn how to solve the problems that reside in microprocessor operations.
CPU ESSENTIALS: The basic requirements for any CPU are Buses and Processor modes. A typical diagram of a processor
is shown in Figure below.
, The Buses: - Usually the BUS is the common means of sharing data and this data transfer is done between all the
devices connected to it. The Buses are also called processor signals. The several sets of these signals are divided into
three main sets, mainly:
i. Data bus
ii. Address bus
iii. Control bus
i. Data bus: - This BUS is responsible for the to and fro movement of information in the CPU. It acts as a measure of CPU
performance. It is also used to carry data in and out of the CPU at any given time. As shown in figure 1.1 the data BUS is
used to carry the information from CPU to RAM, ROM and I/O units as well as among Timing and control, BUS interface
and ALU. The data lines are usually represented by “D” prefix (D0, D1, D2, and D3 … Dn).
ii. Address bus: - This BUS is used to define address in the CPU. It is also called the memory BUS. The Address BUS does
not carry the actual data but carries the specific address of that data. The address BUS measures the data in terms of
address lines. For example, the CPU with address lines= 10 may have address 210 = 1024 bytes. The “A” prefix (A0, A1,
A2, A3 … An). is generally used to represent address lines.
iii. Control BUS: This BUS is also called as timing and control BUS. It is used to control and coordinate CPU operations.
The various signals are read, write, interrupt, and acknowledge; parity checking, cache operation and power control and
management.
Processor modes: Before we proceed to the CPU concepts and their architecture, it would help you to have a brief
introduction to some of the concepts of processor modes. In generic terms, mode is a way that creates a system for
itself for its processor creation and operations. Processor mode is responsible for managing and controlling the system
memory and its use. Processor modes are classified into three types as:
i. Real mode
ii. Protected mode
iii. Virtual real mode
i. Real Mode: This mode operates CPU in a limited environment. The real mode has the advantage of accessing speed.
It is compatible with Intel 8088 chips. All processors can support real mode. Computers normally boot up in real mode or
DOS mode.
ii. Protected Mode: This mode used in modern multitasking operating systems was first implemented in 80826.
Protected Mode has several advantages. o It offers faster access to memory
1.It supports multitasking facility that manages the operating
2. System in the execution of many programs at a time.
3.There is no limit to accessing the memory.
4. It allows the computer to use additional memory whenever
5. Needed along with the support of virtual memory.
iii. Virtual Real Mode: This mode of operation is the enhancement of protected mode. Protected mode is used to run
graphical multitasking OS like windows. If you want to run DOS program in the windows system, then you would have to
use the virtual real mode. This is because the necessity of running DOS program on real mode and not in protected
UNIVERSITY: MANIPAL UNIVERSITY JAIPUR
TOPIC: The CPU
INTRODUCTION: To know the meaning of CPU or the way to troubleshoot it. You must know the physical and
mechanical concepts of PC. PC or personal computer is a small digital device made from Microprocessor chip and
designed especially for the use of individual person. PC is not a single device. It is the combination of different
components and devices. Before we start troubleshooting a PC, we must understand these different devices. In this unit
you will study one of those devices in detail and learn how to troubleshoot. You may feel amused to read the word
troubleshooting without knowing the meaning of it. Troubleshooting is a way of detecting the problem in the PC or the
cause of the problem and fixing the problem so that the PC can function according to the needs of the user. This
problem may be from any of the components of the PC.
Since all these components are interrelated the failure in one device may cause the whole system to stop working or
work haphazardly. Troubleshooting is a technique to solve this problem and make the system work appropriate. The
different components of PC are CPU, motherboard, memory, hard drives, monitor, ports, adapter USB, etc. which you
will be studying one by one in later units. In this unit you will learn how to trouble shoot the CPU, which is an essential
part of a computer. In fact, it functions as a brain to the system. We often consider CPU to be a synonym for cabinet.
However, you should keep in mind that there is a vast difference between the two. The CPU is the controller while the
cabinet is a component that holds CPU and memory along with Buses for data flow. Integrated circuit technology has
realized the importance of the Central Processing Unit (Processor) as it is expected to perform three major functions.
They are mathematical calculations, logical comparisons, and data manipulation.
Though the concept of central processing is not new, it was only after the integration of central processing functions into
a single silicon chip, that it became well known as CPU. In the mid-1970s, this single silicon chip referred to as
microprocessor chip, was instrumental in enhancing the speed and performance of the computer greatly. To become an
effective techie, you should know the essential components of CPU. You should also know the important specifications
of CPU and its features. This unit will not only give you an insight into the evolution of CPU and its capabilities but also
help you to learn how to solve the problems that reside in microprocessor operations.
CPU ESSENTIALS: The basic requirements for any CPU are Buses and Processor modes. A typical diagram of a processor
is shown in Figure below.
, The Buses: - Usually the BUS is the common means of sharing data and this data transfer is done between all the
devices connected to it. The Buses are also called processor signals. The several sets of these signals are divided into
three main sets, mainly:
i. Data bus
ii. Address bus
iii. Control bus
i. Data bus: - This BUS is responsible for the to and fro movement of information in the CPU. It acts as a measure of CPU
performance. It is also used to carry data in and out of the CPU at any given time. As shown in figure 1.1 the data BUS is
used to carry the information from CPU to RAM, ROM and I/O units as well as among Timing and control, BUS interface
and ALU. The data lines are usually represented by “D” prefix (D0, D1, D2, and D3 … Dn).
ii. Address bus: - This BUS is used to define address in the CPU. It is also called the memory BUS. The Address BUS does
not carry the actual data but carries the specific address of that data. The address BUS measures the data in terms of
address lines. For example, the CPU with address lines= 10 may have address 210 = 1024 bytes. The “A” prefix (A0, A1,
A2, A3 … An). is generally used to represent address lines.
iii. Control BUS: This BUS is also called as timing and control BUS. It is used to control and coordinate CPU operations.
The various signals are read, write, interrupt, and acknowledge; parity checking, cache operation and power control and
management.
Processor modes: Before we proceed to the CPU concepts and their architecture, it would help you to have a brief
introduction to some of the concepts of processor modes. In generic terms, mode is a way that creates a system for
itself for its processor creation and operations. Processor mode is responsible for managing and controlling the system
memory and its use. Processor modes are classified into three types as:
i. Real mode
ii. Protected mode
iii. Virtual real mode
i. Real Mode: This mode operates CPU in a limited environment. The real mode has the advantage of accessing speed.
It is compatible with Intel 8088 chips. All processors can support real mode. Computers normally boot up in real mode or
DOS mode.
ii. Protected Mode: This mode used in modern multitasking operating systems was first implemented in 80826.
Protected Mode has several advantages. o It offers faster access to memory
1.It supports multitasking facility that manages the operating
2. System in the execution of many programs at a time.
3.There is no limit to accessing the memory.
4. It allows the computer to use additional memory whenever
5. Needed along with the support of virtual memory.
iii. Virtual Real Mode: This mode of operation is the enhancement of protected mode. Protected mode is used to run
graphical multitasking OS like windows. If you want to run DOS program in the windows system, then you would have to
use the virtual real mode. This is because the necessity of running DOS program on real mode and not in protected
