Info-Grade

As we need a highway to travel from one place to another place. Similarly, the input and output of computer system also need a path to transmit data, information and control from one device to another device. The data transmit from input device to CPU, CPU to memory are common examples of system bus.

The path through which data and instruction flow is called bus of computer. It is a collection of wires, chips and slots inside the computer through which data and information are transmit from one part of computer to another.

Normally, Bus is available from 1 bit and above. The width of the bus determines how much data can moved at a time. Nowadays, PATA cables are replaced by SATA cables because of faster and small in size. These are also a way of transferring data and information from HDD to memory. Beside these cables there are numbers of buses inside the computer system (motherboard). There are three types of System bus they are :

1) Address Bus

The pathway through which transmit of address of memory location is called address bus. All types of memory devices have microscopic memory cells which are identified with unique humans known as memory address or memory locations. When the CPU reads data or instruction from memory or writes data to memory, it must specify the address of the memory location it is going to access. Unlike the other buses, the address bus always receive memory location from the CPU. There is one way flow in address bus.

2) Data Bus

The pathway (circuit / chips / wires / slots) through which transmit of data from one memory location to other is called Data Bus. When the CPU fetches data from memory, it first output the memory address on its address bus. Then the data bus. When writing data to memory, the CPU first outputs the address onto the address bus, then output the data onto the data bus. Memory the reads and stores the data to the proper location. The data flows in bidirectional way.

3) Control Bus

The pathway (circuit / chips / wires / slots) through which transmit of control signal to operate and control devices and software is called control bus. It is different from other two buses. The control bus is the collection of individual control signals for timing and controlling function sent by the control unit to other unit of the system. These signals indicate where data is to read or written, whether the CPU is accessing memory or an input/output device, and whether the I/O device or memory is ready to transfer data.

Generations of Computer (Computer note)

Based on the period of development and the features incorporated the computer are classified into different generations from first generation to fifth generation computers.

First Generation Computer

Computers which were made approximately between 1941 and 1955 A.D. are classified as the first generation computer. Vacuum Tube is the main technology, which was developed by Lee de forest in 1908 A.D.

Technology : Vacuum Tube
Processing Speed : processing speed was measured in millisecond
I/O Devices : Punch card was used as input / output devices
Compute Type : Computers were electron mechanical
Memory : Vacuum tube was used as memory device
Storage device : First punch card and later magnetic drum
Operation Mode : Computer should be setup manually as there was no operating system
Reliability and Accuracy : Not fully reliable and accurate
Programming language : Machine level language
Size and cost : Very large in size and expensive
Availability : available to the military purpose and university research only
Power and Heat : Consumed a lot of a electricity and emitted a lot of heat
Portability : Computer were not portable
Example : Mark I, ABC, ENIAC etc.

Second Generation Computer

Computer which were made approximately between 1955 to 1964 and having the transistor and diodes as main memory device are classified as the second generation computer. Transistor was designed by Walter Brattain, John Bardeen and William Sockley in 1947 A.D.

The main features of computer generation are as follows.

Technology : Transistor (Main component)
Processing Speed : Measured in Microsecond
I/O Devices : punch card was used as input / output device
Memory: Magnetic core memory is used as internal memory
Storage device : Magnetic tape
Operation mode : Should set up manually as there was not os.
Reliability and Accuracy : More reliable and accurate then first generation computer.
Programming language : Assembly and high Level language such as FORTRAN, ALGOL, COBOL etc.
Size & cost : Smaller and less expensive then first generation
Availability : Available for general purpose
Power consumption and Heat : Power consumption and heat emission was less then first generation computer.
Portable : Not portable
IBM 1401, ICL 2950/10, IBM 1620 etc.

Third Generation Computer

The computers which were made approximately between 1964 to 1975 and having IC's technology as memory and processing devices are classified as third generation computer. The first IC was developed by Jack Kilby and Robot Noyce in 1985. Later Robert Noyce established Intel company.

Technology : IC (Integrated Circuit)
Processing Speed : Faster than previous generation computer
I/O devices : Keyboard and Monitor
Computer Type : Electronic
Memory : Semiconductor memory (Primary memory)
Storage Devices : Magnetic disk (Secondary memory)
Operation Mode : Os was introduced for automatic and multi programming.
Reliability and accuracy : Fully reliable and accurate
Programming language : High level language for computer programming
Size and cost : Smaller in size and less expensive then previous generations of computer
Availability : Available for general purpose as well as for personal use.
power consumption and heat emission : Power consumption and heat emission was less than previous generation computer
Potable : Become portable computer because of development of Desktop and Laptop computer
Example : IBM 360 Series, ICL 1900 etc, UNIVAC etc.

Fourth Generation Computer

The computer which were made approximately between 1975 to till now and having microprocessor as CPU and VLSI and ULSI technology in IC as memory device and classified as fourth generation computer.

- Microprocessor is a chip in which millions of components are integrated together in different layers.

- First commercial microprocessor was Intel 4004 made by Intel corporation in 1971 AD. It was 4 bit processor.

The main features of fourth generation computer are

Technology : IC's and Microprocessor
Processing speed : Faster then previous generations
I/O devices : Fourth refined and invented various devices such as scanner, touch screen, printer etc.
Computer type : Electronic
Memory : Semiconductor memory with huge capacity
Storage device : Magnetic and optical disk with large storage capacity for secondary storage device.
Operation mode : Multi programming, multi processing, multimedia and distributed operating system become possible.
Reliability and accuracy : Fully reliable and accurate
Programming language : advance HLL and 4GL for application and database programming have been used.
Size and cost : Smaller and less expensive then previous generations of computer
Availability : General purpose as well as special purpose
Power consumption and heat emission : It has been less then previous generation of computer
Portable : Because portable off development of personal or Desktop computer, Laptop, Notebook, PDA etc.
Example : Acer ASPIRE 5741, Apple MacBook Air, Dell Inspiration 1400 etc.

Fifth Generation Computer

Although the computer of this generation have not come yet in reality, but computers scientist are trying since 1990 A.d. It is said that the computer of this generation will use AI (Artificial Intelligence) and bio-chips as memory devices so that they can think and decide this like a human being.

Features of fifth generation computer are as follows

They will be super conductor memory like bio-chips that the speed will be very fast.
The computer will be intelligent and knowledge base because of AI.
Instead of HLL, natural languages will be used such as English, Nepali, Hindi for giving instruction
this computer will have power of seance, logic and decision making capacity

Micro Operation (Computer Architecture)

In computer CPU the micro-operations are detailed low-level instructions which is used in some designs to implement complex machine instructions. Usually, micro-operations perform basic operations on data stored in one or more register, including transferring data between registers or between registers and external buses of the CPU and performing arithmetic or logical operations on registers. The execution of micro-operations is performed under control of the CPU’s control unit which decides on their execution while performing various optimizations such as reordering, fusion and caching of the operations.

The operations executed on data stored in registers are called micro-operations. A micro-operation is an elementary operation performed on the information stored in one or more registers. The functions built into registers are examples of micro operations, They are Shift, Load, Clear, Increment, add, subtract, complement, and, or, xor etc ..

There are Four Types of Micro Operations

1. Register transfer micro-operations

2. Arithmetic micro-operations

3. Logic micro-operations

4. Shift micro operations

1) Register transfer micro operation

Register transfer language is a kind of intermediate representation (IR) that is very close to assembly language, such as that which is used in a compiler. It is used to describe data flow at the register transfer level of an architecture. It is a convenient tool for describing the internal organization of digital computers in concise and precise manner. These types of micro operations are used to transfer binary information from one register to another. Often the names indicate function:

MAR – Memory Address Register
PC - Program Counter
IR - Instruction Register

In this case the contents of register R1 are copied (loaded) into register R2

2) Arithmetic Micro-Operations

These micro-operations are used to perform some arithmetic operations on numeric data stored in the registers. A micro operation is an elementary operation performed on the information stored in one or more registers. The micro operation in digital computers is of 4 types: Addition, Subtraction, Increment, and Decrement

Addition:-

R1 = A + B

R3 = R1 + R2

Subtraction: -

R1 = R2 – R3

Subtraction operation also can be performed on 2’s complement R = R1 + R2’ + 1

Increment:-

R1 = R1 + 1, R2 = R2 + 1

Decrement:-

R1 = R1 – 1, R2 = R2 – 1

3) Logic Micro-Operations

These micro operations are used to perform bit style operations or manipulations on non-numeric data. In computer CPU, micro-operations are the functional or atomic operations of a processor. Logic micro operations are bit-wise operations, i.e., they work on the individual bits of data. These are useful for bit manipulations on binary data and also useful for making logical decisions based on the bit value.

R1 = R1 XOR R2

R2 = R3 AND R4

4) Shift Micro-Operations

These are used for serial transfer of data. That means we can shift the contents of the register to the left or right. In the shift left operation the serial input transfers a bit to the right most position and vice versa.

There are three types of shifts as follows:
a) Logical Shift

It transfers 0 through the serial input. The symbol "shl" is used for logical shift left and "shr" is used for logical shift right.

              R1 ← she R1
              R1 ← she R1

The register symbol must be same on both sides of arrows.

b) Circular Shift

This circulates or rotates the bits of register around the two ends without any loss of data or contents. In this, the serial output of the shift register is connected to its serial input. "cil" and "cir" is used for circular shift left and right respectively.

              R1 = cir R1
              R2 = cil R2

c) Arithmetic Shift

This shifts a signed binary number to left or right. An arithmetic shift left multiplies a signed binary number by 2 and shift left divides the number by 2. Arithmetic shift micro-operation leaves the sign bit unchanged because the signed number remains same when it is multiplied or divided by 2.

R ← ashl R (arithmetic shift left R (register))

R ← ashr R (arithmetic shift right R (register))

RISC and CISC Processors

RISC (Reduced Instruction Set Computer) Processor

RISC is known as Reduced instruction Set Computer. It is a type of microprocessor that has limited number of instructions. It can execute it's instructions very fast because instructions are very small and simple.

RISC chips require fewer transistors which make them cheaper to design and produce. Most Instructions complete in one cycle, which allows the processor to handle many instructions at same time. In this type of processor, instructions are register based and data transfer takes place from register to register.

Features of RISC

Simple and small instruction
Instruction come under size of one word
Instruction take single clock cycle to get executed
Simple addressing modes
Less data types
Pipeline can be achieved
More number of general purpose register

CISC (Complex Instruction Set Computer) Processor

CISC is known as Complex Instruction Set Computer. It was first developed by Intel corporation. It contains large number of complex instructions. In this processor instructions are not register based and instructions cannot be completed in one machine cycle. Data transform is from memory to memory. Micro programmed control unit is found in CISC. It also have variable instruction format.

Features of CISC

Complex instruction, hence complex instruction decoding
Instruction may take more than single clock cycle to get executed
Instruction are larger than one word size
Complex addressing mode
More data types

Difference Between CISC and RISC

RISC	CISC
It has Large set of instructions with variable formats Data transfer is from register to register. Instruction are register based. It takes less memory access It includes single clock. Instructions are reduced and simple.	It has small set of instructions with fixed format Data transfer is from memory to memory Instructions are not memory based. It takes more memory access It includes multi clocks. Instructions are complex.

Info-Grade

Computer Fundamental

Hardware & Networking

Applications

Programming

Random Post

Automata theory (Discrete Structure Note)

View Connected WiFi Password with Single line DOS Command