Unit-1: Computer Organization
Computerorganization:
It refers to the operational units and their instruction that realize architectural
specification. Computer organizational attributes include hardware details
transparent to the programmer, such as control signals, interface between the
computer memory and input/output mechanism.
Example:
• Building Capacity of 3000 people
• How building will reach the ability of 3000 people
3.
Computer Organization …
ByOrganization view, the computer is divided into three components:
• the processor: the main part of the computer. Its task is to execute the
program using the control unit (CU)
• the memory: simply stores the information written in it
• the I/O processor: interface the computer to access the outside world
The Control Unit: 2 parts
• the Arithmetic and Logical unit (ALU), and
• the registers
4.
Computer Organizations…
Registers
Register areused to quickly accept, store, and transfer data and instructions that
are being used immediately by the Central Processing Unit (CPU).
Types of Registers
• Accumulator (AC)
• Data Register (DR)
• Address Register (AR)
• program counter (PC)
• Memory Data Register (MDR)
• Index register (IR)
• Memory Buffer Register (MBR)
5.
Registers Types …
•Memory Address Register (MAR)
• Holds memory address of data and instructions
• Used to access data and instructions from the memory
• CPU places the address of required memory locations in MAR
• Program Counter
• Also known as Instruction Pointer
• Sometimes called Instruction Address Registers (IAR)
• It is a 16-bit special function processor Register
• It keeps tracks of the next memory address of the instruction to be executed
• Accumulator
• Used for storing the results that are produced by the system
6.
Register Types …
•Memory Data Register (MDR)
• It is the register of the Control Unit
• Contains the data to be stored or fetched in the computer storage e.g. RAM
• It acts like a buffer and holds anything that is copied from the memory ready
for the use of the processor
• It is a two way registers
• It stores data fetched from the memory
• Data to be written from other CPU registers could be placed on MDR
• The Memory Data Register is half minimal Interface between a micro program
and computer storage
7.
Register Types …
•Index Register (IR)
• Hardware element which holds a number that can be added or removed
from the address portion of a computer instruction to form an effective
address
• Also known as Base Register
• It is a processor register for modifying operand addresses during the run
of a program
• Memory Buffer Register (MBR)
• Holds the contents of data or instruction read from or written to memory
• Data Register
• Used to temporarily store data being transmitted to and fro a peripheral
device
• A fast storage units where a few pieces of information can be stored temporarily
until needed
8.
Computer Organization…
Registers areused by the CPU for performing some required
operations.
• A user gives some inputs to the system
• the input is stored in the Registers and
• the system gives us the results after processing the inputs.
• The result is also stored in the Registers so that they are used by the CPU for
processing the data which is given by the user
Registers in the Memory Hierarchy
• Memory Hierarchy is an enhancement to organize the memory such
that it can minimize the access time
• The Memory Hierarchy was developed based on a program behavior
known as Locality of References.
Computer Organization…
Operations Performedby Registers
• Fetch: Registers use the Fetch Operation to take the instructions
given by the user and those stored into the Main Memory.
• Decode: The Decode Operation is used for interpreting the
instructions. In order words, it means the instructions are
decoded by the CPU which then determines the operation to be
performed on the instructions.
• Execute: The Execute Operation is performed by the CPU. The
Results that are produced by the CPU are then stored into the
memory after which they are displayed on the user Screen.
12.
Computer Organization…
Register Organization
Theyserve two functions:
1. User-Visible Registers - enable the machine- or assembly- language
programmer to minimize main-memory references by optimizing use of registers
2. Control and Status Registers - used by the control unit to control the
operation of the CPU and by privileged, OS programs to control the
execution of programs
13.
Ports, Codes, Dataand Stack Segments
Ports
• A Computer Port is an interface or a point of connection between the computer
and its peripheral devices.
• Some of the common peripherals are mouse, keyboard, monitor or display unit,
printer, speaker, flash drive
• The main function of a computer port is to act as a point of attachment
• A computer port is also called as a Communication Port
• the female end of the connector is referred to as a port and it usually sits on the
motherboard
• communication ports can be divided into two types
• Serial Ports and
• Parallel Ports
14.
Ports…
A serial port
Thisis an interface through which peripherals can be
connected using a serial protocol which involves the transmission
of data one bit at a time over a single communication line
A parallel port
on the other hand, is an interface through which the
communication between a computer and its peripheral device is in
a parallel manner i.e. data is transferred in or out in parallel using
more than one communication line or wire. Printer port is an
example of parallel port
15.
Ports…
Types of Portsand Applications… PS/2
• PS/2 connector is developed by IBM for connecting mouse and keyboard
• It was introduced with IBM’s Personal Systems/2 series of computers and
hence the name PS/2 connector
• PS/2 connectors are color coded as purple for keyboard and green for mouse
• PS/2 is a 6-pin mini DIN (Deutsche Institut fuer Normung) connector
• DIN is a German standardization group
• It is still sometimes found on all IBM compatible computers.
16.
Types of Portsand Applications … PS/2
Computer keyboards, computer mice, network routers, video appliances, and Apple serial
devices are a few examples of hardware devices that may use a DIN style of connector
The right illustration is of the actual PS/2 male
connection with its pin layouts.