The History Of Central Processing Unit

Published Date: 02 Nov 2017

A computer is an electronic device that people used to accept information. Information is in the digitalized data form. Computer gives sequence of instructions on the data and how the data is to be processed. Computer will based on the program and manipulates it for some result. Nowadays, every family also will have a least 1 computer. Computer is very important in this world for everyone. However, desktop and laptop computers that most people use that can often used to refer to the computer.

Central Processing Unit (CPU)

Processor, also called the Central Processing Unit (CPU), interprets and carries out the basic instructions that operate a computer. Processor contains a control unit that directs and coordinates most of the operations. Motherboard is something called a system board, is the main circuit board of the system unit. The Processor Chip is build on the motherboard.

A computer can have one or more than one Central Processing Unit. It is called Multiprocessing. Some microprocessor can have more than one Central Processor Unit in a single silicon chip which is Multi-Core Processors.

BUS

In Computing, BUS is a subsystem. That use to transfer data between computers or between components in the computer such as memory, sound system and video system to the computer’s Central Processing Unit. If no bus port, graphics card cannot plug into a computer. Computer's monitor would be useless, because that route cannot communication between the card and the computer's Central Processing Unit. This is a physical connection.

2.0 Central Processing Unit

Central Processing Unit is the hardware component that within a computer that uses to control the computer operation. It is the key component of the computer system, same like human brains which interpret and execute program instructions. Central Processing Unit performs the basic calculation, logical and I/O operation of the system. In the large machines, Central Processing Unit will required more than one or only one printed circuit board that can getting a best preferment. For the small workstation or personal computer, the Central Processing Unit is a single chip that we called Microprocessor. The Central Processing Unit is small and square. It contains multiple metallic connectors and pin on the underside. On the motherboard, Central Processing Unit pin side down and it is inserting into a socket.

2.1 History of Central Processing Unit

The history of Central Processing Unit is often referred to the different generation of computing device. In every generation also will have a top or faster Central Processing Unit to meet the human needed. Evolution of Central Processing Unit will change the way of how computer operate, how the computer increase the result display, computer become smaller, computer become cheaper, computer become more powerful and become more efficient to the computer user who request high technologies of computer. Nowadays, only five generation of Central Processing Unit that I knew in my knowledge which is Vacuum Tubes, Transistors, Integrated Circuits, Microprocessors and Artificial Intelligence.

2.1.1 First Generation (1940 – 1956) Vacuum Tubes

Vacuum Tubes are the first generation of Central Processing Unit. The first computer is using Vacuum Tubes and Magnetic Drums for memory. It is very big size and it uses the entire rooms. So, it is very expensive. When this Central Processing Unit is working, it must use a great deal of electricity. So, it will make the Central Processing Unit generated a lot of heat. Sometimes, computer will over heat. It is the way that often the cause of computer malfunctions. First generation computer are relied to the machine or programming language. The computer only understood the lowest level machine of programming language. First generation computer only can solve only one problem at a same time. In this generation, computer input was using the punched cards or paper tape and the output was displayed and printouts on the punched cards or the paper tape.

The example of the first generation computers devices are UNIVAC and ENIAC. The first commercial computer was the UNIVAC. It is use on the U.S. Census Bureau in 1951 for delivered to a business.

2.1.2 Second Generation (1956 – 1963) Transistors

Transistors are the second generation Central Processing Unit. It is replaced the first generation Central Processing Unit. Transistor was invented in 1947, but it is did not widespread use in the computer. Transistor was far greater to the vacuum tubes. Transistor made the computers to become cheaper, become smaller, faster than the first generation Central Processing Unit, more energy efficient and transistor is more reliable than the vacuum tube. Transistors were widespread using in the computer at the late 1950s. But, transistor still has the same problem with the vacuum tube which is generated the heat and easy to make the computer malfunctions. It was a vast improvement. Second-generation computers still using the punched cards to input and printouts the result.

Transistor was using the symbolic or assembly language, which allowed the programmer easy to giving specify instruction only enter some words. Therefore, high level programming language also developed at this generation which is the early version of COBOL and FORTRAN. In transistors, the first computers were developed for the atomic energy industry.

2.1.3 Third Generation (1964 – 1971) Integrated Circuits

Integrated Circuits are the hallmark of the third generation Central Processing Unit. In integrated circuits, user can interact with the computer using keyboards and monitors and interfaced with an operating system. It was not using punched cards and printouts. This integrated circuit can run more than one program at once times. It is run with the central program that monitored the memory. This is the first computer that the mass audiences are affordable to buy a computer because Integrated Circuit was smaller and cheaper than the Vacuum Tubes and Transistors.

2.1.4 Fourth Generation (1971 – Present) Microprocessors

Microprocessors are brought the fourth generation Central Processing Unit. Microprocessors are far superior to the predecessors. Because it like got a thousands of integrated circuits are build on a single chip. Compare with the first generation central processing unit, we can simple hold microprocessors in our hand. In 1971, the Intel 4004 chip was developed. This processors are located all the components of the computer. From the central processing unit and memory to I/O controls also on a single chip.

In 1981, the first computer form the home user was developed by IBM. In 1984, Macintosh was invented. Therefore, Microprocessors was widespread use on the desktop computer and into many areas of life. Many products were using the microprocessors. As these small processors made the computer became more powerful and cheaper. So, it can link the computer together to form networks. In this trend, the internet is growing up. Therefore, the fourth generation computers also saw the development of Graphical User Interface (GUI), mouse and the handheld devices. It made the user can easy interact with the computer. User also can interact with another via computer and internet.

2.1.5 Fifth Generation (Present and Beyond) Artificial Intelligence

Based on the Artificial Intelligence is the fifth generation Central Processing Unit. This is the Central Processing Unit that still in development. But still have some application are being used today, such as voice recognition. By the way, it is still in process. The goal of Artificial Intelligence is develop a device that can respond to input the natural language and that is capable of learning.

2.2 Design of the Central Processing Unit

Central Processing Unit divided into 3 major sections which are Arithmetic/Logic Unit (ALU) and Control Unit. All this 2 sections are work together to perform the sequences of micro-operations needed.

2.2.1 Arithmetic/Logic Unit (ALU)

Arithmetic/Logic Unit is performing the Arithmetic and Logic Operation in the computer. This is the part of the computers that operate and performs all the arithmetic computations which is addition/multiplication and all comparison operations.

2.2.2 Control Unit

Control Unit giving the instruction to the memory to decode and executes them. Control Unit also will calling on the Arithmetic/Logic Unit when necessary.

2.3 Conclusion

To design a CPU, we first develop its instruction set architecture, including its instruction set and its internal registers. We then create a finite state machine model of the micro-operations needed to fetch, decode, and execute every instruction in its instruction set. Then we develop an RTL specification for this state machine.

A CPU contains three primary sections: the register section, consisting of the registers in the CPU’s ISA as well as other registers not directly available to the programmer, the ALU, and the control unit. The micro-operations in its RTL code specify the functions to be performed by the register section and the ALU. These micro-operations are used to design the data paths within the register section, including direct connections and buses, and the functions of each register. The micro-operations also specify the functions of the ALU. Since the ALU must perform all of its calculations in a single clock cycle, it is constructed using only combinatorial logic.

The conditions under which each micro-operation occurs dictate the design of the control unit. The control unit generates the control signals that load, increment, and clear the registers in the register section. The control unit also enables the buffers used to control the CPU’s internal buses. The function to be performed by the ALU is specified by the control unit. By outputting the control signals in the proper sequence, the control unit causes the CPU to properly fetch, decode, and execute every instruction in its instruction set.

3.0 BUS

A bus is a communication pathway connecting two or more components of devices. It is a means of getting data from one point to another, point A to point B, one device to another device, or one device to multiple devices. The bus includes not only the actual capability to transfer data between devices, but also all appropriate signaling information to ensure complete movement of the data from point A to point B. To avoid loss of data, a bus must include a means of controlling the flow of data between two devices, in order to insure that both devices are ready to send and/or receive information. Finally, both ends must understand the speed with which data is to be exchanged. A bus provides for all of these elements, and it includes a port definition to allow physical interfacing or connecting of two or more devices.

3.1 Bus Interconnection

A bus is a set of electrical wires that conveys a single bit of information along each line. Two types: point-to-point, and multipoint buses.

Diagram of Bus lines

Bus lines are usually classified into:

Address: Identify the source or destination of data. Example: Memory location generated by CPU

Data: Carry data information. Example: Data from a location in memory

Control: Transmit command and timing information

Address Bus

The address bus consists of 16, 20, 24, or 32 parallel signal lines. On these lines the CPU sends out the address of the memory location that is to be written to or read from. The number of memory locations that the CPU can address is determined by the number of address lines. If the CPU has N address lines, then it can directly address 2N memory locations. CPU with 16 address lines can address 65,536 memory CPU with 20 address lines can address 1,048,576 locations When the CPU reads data from or writes data to a port, it sends the port address out on the address bus.

Data Bus

The data bus consists of 8, 16, or 32 parallel signal lines. The data bus lines are bidirectional. Many devices in a system will have their outputs connected to the data bus, but only one device at a time will have its outputs enabled. Any device connected on the data bus must have three-state outputs so that its outputs can be disabled when it is not being used to put data on the bus.

Control Bus

The control bus consists of 4 to 10 parallel signal lines. The CPU sends out signals on the control bus to enable the outputs of addressed memory devices or port devices. Typical control bus signals are Memory Read, Memory Write, I/O Read, and l/O Write. To read a byte of data from a memory location, the CPU sends out the memory address of the desired byte on the address bus and then sends out a Memory Read signal on the control bus. The Memory Read signal enables the addressed memory device to output a data word onto the data bus. The data word from memory travels along the data bus to the CPU.

If one module wishes to send data to another, it must:

Obtain use of the bus

Transfer data via the bus

If one module wishes to request data from another, it must:

Obtain use of the bus

Transfer a request to the other module over control and address lines

Wait for second module to send data

Typical physical arrangement of a system bus

A number of parallel electrical conductors

Each system component (usually on one or more boards) taps into some or all of the

bus lines (usually with a slotted connector)

System can be expanded by adding more boards

A bad component can be replaced by replacing the board where it resides

3.2 Single Bus Structure and Multi-Bus Structure

Single Bus structure and multiple bus structures are types of bus or computing. A bus is basically a subsystem which transfers data between the components of a computer component either within a computer or between two computers. It connects peripheral devices at the same time. A multiple Bus Structure has multiple inter connected service integration buses and for each bus the other buses are its foreign buses. A Single bus structure is very simple and consists of a single server. A bus cannot span multiple cells. And each cell can have more than one bus. Published messages are printed on it. There is no messaging engine on Single bus structure.

Using a multi-bus architecture will really improve the speed and also increase the performance of your processor in execution of different instructions because using a multi- bus architecture will help in such a way that one device would be connected to one bus or less devices would be connected to one bus rather than in single bus architecture more devices would be attached to single bus. Hence, the delay in execution of instructions of the devices would be really less because in case of single bus architecture the delay is greater. Actually when an instruction is transferred by the bus to the processor from a specific device, the other devices wait for the bus to be free and transfer their instructions when the bus becomes free. Hence each device has to wait for the bus to be free and hence a delay comes in the execution of the instructions. Now in multi bus architecture less devices are connected to a single bus hence the delay in the execution of instructions is less.

Single Bus Problems

Lots of devices on one bus lead to:

Physically long buses

Propagation delays – Long data paths mean that co-ordination of bus use can adversely affect performance

Reflections/termination problems

Aggregate data transfer approaches bus capacity

Slower devices dictate the maximum bus speed

Multiple Bus Benefits

Isolate processor-to-memory traffic from I/O traffic

Support wider variety of interfaces

Processor has bus that connects as direct interface to chip, then an expansion bus interface interfaces it to external devices (ISA)

Cache (if it exists) may act as the interface to system bus

3.3 Bus Transmission

Timing

Bus Timing is CO-ordination of events on bus. Bus timing divided into two types which are Synchronous and Asynchronous. Synchronous is controlled by a clock. Asynchronous handled by well-defined specifications, i.e. a response is delivered within a specified time after a request.

Synchronous Bus Timing

Events determined by clock signals

Control Bus includes clock line

A single 1-0 cycle is a bus cycle

All devices can read clock line

Usually sync on leading/rising edge

Usually a single cycle for an event

Analogy – Orchestra conductor with baton

Usually stricter in terms of its timing requirements

Asynchronous Timing

Devices must have certain tolerances to provide responses to signal stimuli

More flexible allowing slower devices to communicate on same bus with faster devices.

Performance of faster devices, however, is limited to speed of bus

Asynchronous Timing – Read

Asynchronous Timing – Write

3.4 Conclusion

Computer Bus is a set of physical connections (cables, printed circuits, etc.) which can be shared by multiple hardware components in order to communicate with one another. 

The purpose of buses is to reduce the number of "pathways" needed for communication between the components, by carrying out all communications over a single data channel. This is why the metaphor of a "data highway" is sometimes used. 

4.0 Conclusion and Recommendation

Processor, also called the Central Processing Unit (CPU), interprets and carries out the basic instructions that operate a computer. Processor contains a control unit that directs and coordinates most of the operations.

Because our computer has a bus, we are able to connect components such as memory, sound systems and video systems to our computer's CPU (central processing unit).

In my opinion, Central Processing Unit and Computer Bus is very important for our computer. So, upgrade the CPU and Bus to the newer version can make our computer performs better.