STUCOR APP
Computer Architecture and Organization Full Notes - STUCOR APP
UNIT I BASIC STRUCTURE OF A COMPUTER SYSTEM 9
Functional Units – Basic Operational Concepts – Performance – Instructions: Language of the Computer –
Operations, Operands – Instruction representation – Logical operations – decision making – MIPS Addressing.
ALU or DATAPATH UNIT
It performs the arithmetic operations.
It is also called as brawn of the processor.
The entire operation can be done with the help of registers.
Registers are faster than memory.
Registers can hold variables and intermediate results.
Memory traffic is reduced, so program runs faster.
CONTROL UNIT
It is also called as a brain of the processor.
It fetches and analyses the instructions one-by-one and issue control signals to all
other units to perform various operations.
For a given instruction, the exact set of operations required is indicated by the control
signals. The results of instructions are stored in memory.
The component of the processor that commands the datapath, memory, and I/O
devices according to the instructions of the program.
MEMORY UNIT
Memory is nothing but a storage device. It stores the program and data.
It is divided into ‘n’ number of cells. Each cell is capable of storing one bit information
at a time.
There are 2 classes of memory.1.Primary 2.Secondary.
Primary Memory
It is made up of semiconductor material. So it is called Semiconductor memory
Data storage capacity is less than secondary memory.
Cost is too expensive than secondary memory.
CPU can access data directly. Because it is an internal memory.
Data accessing speed is very fast than secondary memory.
Ex.RAM & ROM
RAM ROM
Random Access Memory Read Only Memory
Volatile memory Non volatile memory
Data lost when the power turns off and that is It retains data even in the absence of a power
used to hold data and program while they are source and that is store programs between
running. runs.
Temporary storage medium Permanent storage medium
User perform both read and write operation User can perform only read operation
RAM: There are two types of memory available namely, 1. SRAM 2. DRAM
SRAM DRAM
Static RAM Dynamic RAM
Information is stored in 1 bit cell called Flip Information is represented as charge across a
Flop. capacitor
2
2021 – 2022
,STUCOR
EC8552APP
– COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
Information will be available as long as power It retains data for few ms based on the charge
is available of capacitor even in the absence of a power
No refreshing is needed Refreshing is needed
ess packaging density High packaging density
More complex Hardware Less complex hardware
More expensive Less expensive
No random access Random access is possible
Access time 10 ns Access time 50 ns
Cache Memory: A small, fast memory that acts as a buffer for a slower, larger
memory. Secondary memory
Secondary memory (Nonvolatile storage) is a form of storage that retains data
even in the absence of a power source and that is used to store the programs between
runs.
It is made up of magnetic material. So it is called magnetic memory.
Data storage capacity is high than primary memory.
Cost is too low than primary memory.
CPU cannot access data directly. Because it is an external memory.
Data accessing speed is very slow than primary memory.
Ex. Magnetic disk, Hard Disk, CD, DVD, Floppy Disk
Magnetic Disk
It consists of a collection of platters, which rotate on a spindle at 5400 revolution/min.
The metal platters are covered with magnetic recording material on both sides.
Also called hard disk. A form of nonvolatile secondary memory composed of
rotating platters coated with a magnetic recording material.
Because they are rotating mechanical devices, access times are about 5 to 20
milliseconds and cost per gigabyte in 2012 was $0.05 to $0.10.
Optical Disk: Include both Compact Disk (CD) and Digital Video Disk(DVD).
Read-Only CD/DVD
Data is recorded in a spiral fashion, with individual bits being recorded by burning
small pit.
The disk is read by shining a laser at the CD surface and determining by examining
the reflected light whether there is a pit or flat surface.
Rewritable CD/DVD
Use different recording surface that as a crystal line, reflective materials, pits are
formed that are not reflective.
Erase CD/DVD
The surface is heated and cooled slowly, allowing an annealing process to restore the
surface recording layer to its crystalline structure.
Flash Memory
A nonvolatile semiconductor memory. It is cheaper and slower than DRAM but more
expensive per bit and faster than magnetic disks. Access times are about 5 to 50
microseconds and cost per gigabyte in 2012 was $0.75 to $1.00.
OUTPUT UNIT
A mechanism that conveys the result of a computation to a user, such as a display, or to
another computer.
3
2021 – 2022
,STUCOR APP
EC8552 – COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
Liquid Crystal Display
A display technology using a thin layer of liquid polymers that can be used to transmit or
block light according to whether a charge is applied.
All laptops and desktop computers use Liquid Crystal Display (LCD) to get a thin, low-
power display. A tiny transistor switch at each pixel to control current and make sharper
images.
The image is composed of a matrix of picture elements or pixels, which can be
represented as a matrix of bits called bitmap.
Depending on the size of the screen and the resolution, the display matrix ranges in size
from 640*480 to 2560*1600.
A red, green, blue (RGB) associated with each dot on the display determines the intensity
of the three color components in the final image.
Pixel: The smallest individual picture element. Screens are composed of hundreds of
thousands to millions of pixels, organized in a matrix.
BASIC OPERATIONAL CONCEPTS
To perform a given task an appropriate program consisting of a list of instructions is stored in the
memory. Individual instructions are brought from the memory into the processor, which executes
the specified operations. Data to be stored are also stored in the memory. Examples: Add LOCA,
R0
This instruction adds the operand at memory location LOCA, to operand in register R0 &
places the sum into register. This instruction requires the performance of several steps,
1. First the instruction is fetched from the memory into the processor
2. The operand at LOCA is fetched and added to the contents of R0
3. Finally the resulting sum is stored in the register R0
Fig: Connections between the processor and the memory
The fig shows how memory & the processor can be connected. In addition to the ALU & the control
circuitry, the processor contains a number of registers used for several different purposes.
Instruction Register (IR)
Holds the instruction that is currently being executed.
Its output is available for the control circuits which generates the timing signals that
4
2021 – 2022
, STUCOR APP
EC8552 – COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
control the various processing elements in one execution of instruction.
Program Counter PC
This is another specialized register that keeps track of execution of a program.
It contains the memory address of the next instruction to be fetched and executed. Besides
IR and PC, there are n-general purpose registers R0 through Rn-1. MAR PC IR
MEMORY MDR R0 R1 …
1. MAR – (Memory Address Register):- It holds the address of the location to be accessed.
2. MDR – (Memory Data Register):- It contains the data to be written into or read out of
the address location.
Operating steps are
1. Programs reside in the memory & usually get these through the I/P unit.
2. Execution of the program starts when the PC is set to point at the first instruction of
the program.
3. Contents of PC are transferred to MAR and a Read Control Signal is sent to the memory.
4. After the time required to access the memory elapses, the address word is read out of
the memory and loaded into the MDR.
5. Now contents of MDR are transferred to the IR & now the instruction is ready to
be decoded and executed.
6. If the instruction involves an operation by the ALU, it is necessary to obtain the
required operands.
7. An operand in the memory is fetched by sending its address to MAR & Initiating a
read cycle.
8. When the operand has been read from the memory to the MDR, it is transferred from
MDR to the ALU.
9. After one or two such repeated cycles, the ALU can perform the desired operation.
10. If the result of this operation is to be stored in the memory, the result is sent to MDR.
11. Address of location where the result is stored is sent to MAR & a write cycle is initiated.
12. The contents of PC are incremented so that PC points to the next instruction that is to
be executed.
PERFORMANCE
The machine (or CPU) is said to be faster or has better performance running this program if the
total execution time is shorter. When trying to choose among different computers, performance
is an important attribute.
1. Throughput and Response Time
Response time
Response time also called execution time. The total time required for the computer to
complete a task, including disk accesses, memory accesses, I/O activities, operating
system overhead, CPU execution time, and so on.
Throughput or bandwidth
The total amount of work done in a given time. Decreasing response time almost always
improves throughput.
To maximize performance, we want to minimize response time or execution time for some
task. Thus, we can relate performance and execution time for a computer X:
5
2021 – 2022
Computer Architecture and Organization Full Notes - STUCOR APP
UNIT I BASIC STRUCTURE OF A COMPUTER SYSTEM 9
Functional Units – Basic Operational Concepts – Performance – Instructions: Language of the Computer –
Operations, Operands – Instruction representation – Logical operations – decision making – MIPS Addressing.
ALU or DATAPATH UNIT
It performs the arithmetic operations.
It is also called as brawn of the processor.
The entire operation can be done with the help of registers.
Registers are faster than memory.
Registers can hold variables and intermediate results.
Memory traffic is reduced, so program runs faster.
CONTROL UNIT
It is also called as a brain of the processor.
It fetches and analyses the instructions one-by-one and issue control signals to all
other units to perform various operations.
For a given instruction, the exact set of operations required is indicated by the control
signals. The results of instructions are stored in memory.
The component of the processor that commands the datapath, memory, and I/O
devices according to the instructions of the program.
MEMORY UNIT
Memory is nothing but a storage device. It stores the program and data.
It is divided into ‘n’ number of cells. Each cell is capable of storing one bit information
at a time.
There are 2 classes of memory.1.Primary 2.Secondary.
Primary Memory
It is made up of semiconductor material. So it is called Semiconductor memory
Data storage capacity is less than secondary memory.
Cost is too expensive than secondary memory.
CPU can access data directly. Because it is an internal memory.
Data accessing speed is very fast than secondary memory.
Ex.RAM & ROM
RAM ROM
Random Access Memory Read Only Memory
Volatile memory Non volatile memory
Data lost when the power turns off and that is It retains data even in the absence of a power
used to hold data and program while they are source and that is store programs between
running. runs.
Temporary storage medium Permanent storage medium
User perform both read and write operation User can perform only read operation
RAM: There are two types of memory available namely, 1. SRAM 2. DRAM
SRAM DRAM
Static RAM Dynamic RAM
Information is stored in 1 bit cell called Flip Information is represented as charge across a
Flop. capacitor
2
2021 – 2022
,STUCOR
EC8552APP
– COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
Information will be available as long as power It retains data for few ms based on the charge
is available of capacitor even in the absence of a power
No refreshing is needed Refreshing is needed
ess packaging density High packaging density
More complex Hardware Less complex hardware
More expensive Less expensive
No random access Random access is possible
Access time 10 ns Access time 50 ns
Cache Memory: A small, fast memory that acts as a buffer for a slower, larger
memory. Secondary memory
Secondary memory (Nonvolatile storage) is a form of storage that retains data
even in the absence of a power source and that is used to store the programs between
runs.
It is made up of magnetic material. So it is called magnetic memory.
Data storage capacity is high than primary memory.
Cost is too low than primary memory.
CPU cannot access data directly. Because it is an external memory.
Data accessing speed is very slow than primary memory.
Ex. Magnetic disk, Hard Disk, CD, DVD, Floppy Disk
Magnetic Disk
It consists of a collection of platters, which rotate on a spindle at 5400 revolution/min.
The metal platters are covered with magnetic recording material on both sides.
Also called hard disk. A form of nonvolatile secondary memory composed of
rotating platters coated with a magnetic recording material.
Because they are rotating mechanical devices, access times are about 5 to 20
milliseconds and cost per gigabyte in 2012 was $0.05 to $0.10.
Optical Disk: Include both Compact Disk (CD) and Digital Video Disk(DVD).
Read-Only CD/DVD
Data is recorded in a spiral fashion, with individual bits being recorded by burning
small pit.
The disk is read by shining a laser at the CD surface and determining by examining
the reflected light whether there is a pit or flat surface.
Rewritable CD/DVD
Use different recording surface that as a crystal line, reflective materials, pits are
formed that are not reflective.
Erase CD/DVD
The surface is heated and cooled slowly, allowing an annealing process to restore the
surface recording layer to its crystalline structure.
Flash Memory
A nonvolatile semiconductor memory. It is cheaper and slower than DRAM but more
expensive per bit and faster than magnetic disks. Access times are about 5 to 50
microseconds and cost per gigabyte in 2012 was $0.75 to $1.00.
OUTPUT UNIT
A mechanism that conveys the result of a computation to a user, such as a display, or to
another computer.
3
2021 – 2022
,STUCOR APP
EC8552 – COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
Liquid Crystal Display
A display technology using a thin layer of liquid polymers that can be used to transmit or
block light according to whether a charge is applied.
All laptops and desktop computers use Liquid Crystal Display (LCD) to get a thin, low-
power display. A tiny transistor switch at each pixel to control current and make sharper
images.
The image is composed of a matrix of picture elements or pixels, which can be
represented as a matrix of bits called bitmap.
Depending on the size of the screen and the resolution, the display matrix ranges in size
from 640*480 to 2560*1600.
A red, green, blue (RGB) associated with each dot on the display determines the intensity
of the three color components in the final image.
Pixel: The smallest individual picture element. Screens are composed of hundreds of
thousands to millions of pixels, organized in a matrix.
BASIC OPERATIONAL CONCEPTS
To perform a given task an appropriate program consisting of a list of instructions is stored in the
memory. Individual instructions are brought from the memory into the processor, which executes
the specified operations. Data to be stored are also stored in the memory. Examples: Add LOCA,
R0
This instruction adds the operand at memory location LOCA, to operand in register R0 &
places the sum into register. This instruction requires the performance of several steps,
1. First the instruction is fetched from the memory into the processor
2. The operand at LOCA is fetched and added to the contents of R0
3. Finally the resulting sum is stored in the register R0
Fig: Connections between the processor and the memory
The fig shows how memory & the processor can be connected. In addition to the ALU & the control
circuitry, the processor contains a number of registers used for several different purposes.
Instruction Register (IR)
Holds the instruction that is currently being executed.
Its output is available for the control circuits which generates the timing signals that
4
2021 – 2022
, STUCOR APP
EC8552 – COMPUTER ARCHITECTURE AND ORGANIZATION Year / Sem : III / V Department - ECE
control the various processing elements in one execution of instruction.
Program Counter PC
This is another specialized register that keeps track of execution of a program.
It contains the memory address of the next instruction to be fetched and executed. Besides
IR and PC, there are n-general purpose registers R0 through Rn-1. MAR PC IR
MEMORY MDR R0 R1 …
1. MAR – (Memory Address Register):- It holds the address of the location to be accessed.
2. MDR – (Memory Data Register):- It contains the data to be written into or read out of
the address location.
Operating steps are
1. Programs reside in the memory & usually get these through the I/P unit.
2. Execution of the program starts when the PC is set to point at the first instruction of
the program.
3. Contents of PC are transferred to MAR and a Read Control Signal is sent to the memory.
4. After the time required to access the memory elapses, the address word is read out of
the memory and loaded into the MDR.
5. Now contents of MDR are transferred to the IR & now the instruction is ready to
be decoded and executed.
6. If the instruction involves an operation by the ALU, it is necessary to obtain the
required operands.
7. An operand in the memory is fetched by sending its address to MAR & Initiating a
read cycle.
8. When the operand has been read from the memory to the MDR, it is transferred from
MDR to the ALU.
9. After one or two such repeated cycles, the ALU can perform the desired operation.
10. If the result of this operation is to be stored in the memory, the result is sent to MDR.
11. Address of location where the result is stored is sent to MAR & a write cycle is initiated.
12. The contents of PC are incremented so that PC points to the next instruction that is to
be executed.
PERFORMANCE
The machine (or CPU) is said to be faster or has better performance running this program if the
total execution time is shorter. When trying to choose among different computers, performance
is an important attribute.
1. Throughput and Response Time
Response time
Response time also called execution time. The total time required for the computer to
complete a task, including disk accesses, memory accesses, I/O activities, operating
system overhead, CPU execution time, and so on.
Throughput or bandwidth
The total amount of work done in a given time. Decreasing response time almost always
improves throughput.
To maximize performance, we want to minimize response time or execution time for some
task. Thus, we can relate performance and execution time for a computer X:
5
2021 – 2022
