A Microprocessor, popularly known as “computer on a chip” in its early days, is a general purpose central processing unit (CPU) fabricated on a single integrated circuit (IC) and is a complete digital computer (later microcontroller is considered to be more accurate form of complete computer). It is a small but very powerful electronic brain that operates at a blistering speed and is often used to carry out instructions of a computer program in order to perform arithmetic and logical operations, storing the data, system control, input / output operations etc. as per the instructions. The key term in the definition of a microprocessor is “general purpose”. It means that, with the help of a microprocessor, one can build a simple system or a large and complex machine around it with a few extra components as per the application. The main task of a microprocessor is to accept data as input from input devices then process this data according to the instructions and provide the result of these instructions as output through output devices. Microprocessor is an example of sequential logic device as it has memory internally and uses it to store instructions.
The first commercial Microprocessor was released by Intel in year 1971 November named as 4004 (four – thousand – four). It is 4-bit microprocessor.
There are five important components in a microprocessor. They are Arithmetic and Logic Unit (ALU), Control Unit, Registers, Instruction Decoder and Data Bus but the first three are considered significant components. The block diagram of a microprocessor with these basic components is shown below.
The internal structure of a microprocessor is shown below.
Earlier microprocessors made use of Von Neumann architecture where the data and instructions (programs) are stored in the same memory. Even though this architecture is simple, there are many draw backs. One of the major drawbacks is that instruction and data cannot be accessed at the same time as they share a single data bus. This often degrades the overall performance of the device. Later, Harvard architecture is introduced which makes use of separate program and data memories with separate buses so that both data and instructions can be accessed at the same time. Later Modified Harvard Architecture is developed in which the program memory is accessed as if it were data memory.
There are three basic characteristics used to differentiate microprocessors. They are instruction set, bandwidth and clock speed. Instruction set is related to programming of the microprocessor which mainly consists of instructions that a microprocessor can execute. Bandwidth indicates maximum number of bits processed in a single instruction. Clock speed gives no. of instructions a processor can execute per second. Usually clock speed is in MHz (Mega Hertz) or GHz (Giga Hertz). Generally the characteristics bandwidth and clock speed are looked together. The higher the values of both these characteristics, the more powerful the processor is.
Instruction set or instruction set architecture (ISA) also plays an important role in the design and functioning of a processor. Microprocessors are classified as either CISC (Complex Instruction Set Computer) or RISC (Reduced Instruction Set Computer).
CISC architecture consists of full set of instructions that are complex, larger, have more computational power and so on. A single CISC instruction can be used to execute several low-level operations, multi-step operations and multiple addressing modes. The execution time of these instructions is long. Intel’s X86 is an example of CISC architecture. RISC architecture was developed by realizing that instead of using full set of instructions, only the frequently used instructions are sufficient. In this architecture, the instructions are small and highly optimized. RISC processors are used where execution time of the instruction should be less and cost of development is less. The ARM devices are based on ARM architecture which is a subset of RISC.
Evolution of Microprocessor
The microprocessor has become more essential part of many gadgets. The evolution of microprocessors was divided into five generations such as first, second, third, fourth and fifth generation and the characteristics of these generations are discussed below.
EVOLUTION OF MICROPROCESSORS
First Generation Microprocessors
The first generation microprocessors were introduced in the year 1971-1972. The instructions of these microprocessors were processed serially, they fetched the instruction, decoded and then executed it. When an instruction of the microprocessor was finished, then the microprocessor updates the instruction pointer & fetched the following instruction, performing this consecutive operation for each instruction in turn.
Second Generation Microprocessors
In the year 1970, small amount of transistors were available on the integrated circuit in the second generation microprocessors. Examples of the second generation microprocessors are 16-bit arithmetic 7 pipelined instruction processing, MC68000 Motorola microprocessor. These processors are introduced in the year 1979, and Intel 8080 processor is another example of the microprocessor. The second generation of the microprocessor is defined by overlapped fetch, decode and execute the steps. When the first generation is processed in the execution unit, then the second instruction is decoded and the third instruction is fetched.
The difference between the first generation microprocessor and second generation microprocessors was mainly the use of new semiconductor technologies to manufacture the chips. The result of this technology resulted in a fivefold increase in instruction, speed, execution and higher chip densities.
Third Generation Microprocessors
The third generation microprocessors were introduced in the year 1978, was denoted by Intel’s 8086 and the Zilog Z8000. These were 16-bit processors with a performance like mini computers. These types of microprocessors were different from the previous generations of microprocessors in that all main workstation industrialists began evolving their own ISC based microprocessor architectures.
Fourth Generation Microprocessors
As many industries converted from commercial microprocessors to in house designs, the fourth generation microprocessors are entered with outstanding design with a million transistors. Leading edge microprocessors like Motorola’s 88100 and Intel’s 80960CA could issue & retire more than one instruction per clock cycle.
Fifth Generation Microprocessors
Fifth generation microprocessors employed decoupled super scalar processing, and their design soon exceeded 10 million transistors. In fifth generation, PCs are a low-margin, high volume business conquered by a single microprocessor.
Types of Microprocessor
Microprocessors are classified into five types, namely: CISC-Complex Instruction Set Microprocessors, RISC-Reduced Instruction Set Microprocessor, ASIC- Application Specific Integrated Circuit, Superscalar Processors, DSP’s-Digital Signal Microprocessors.
TYPES OF MICROPROCESSORS
Complex Instruction Set Microprocessors
The short term of Complex Instruction Set Microprocessors is CISM and they classify a microprocessor in which orders can be performed together along with other low level activities. These types of processors performs the different tasks like downloading, uploading, recalling data into the memory card and recalling data from the memory card. Apart from these tasks, it also does complex mathematical calculations in a single command.
Reduced Instruction Set Microprocessor
The short term of Reduced Instruction Set Microprocessor is RISC. These types of processors are made according to the function in which the microprocessor can carry out small things in specific command. In this way these processors completes more commands at a faster rate.
Superscalar Microprocessors
Superscalar processor facsimiles the hardware on the processor to perform various tasks at a time. These processors can be used for ALUs or multipliers. They have different operational units and these processors can carry out more than a one command by continuously transmitting several instructions to the extra operational units inside the processor.
The Application Specific Integrated Circuit
The short term of Application Specific Integrated Circuit processor is an ASIC. These processors are used for particular purposes that includes of automotive emissions control or personal digital assistant’s computer. This type of processor is made with proper specification, but apart from these it can also be made with off the shelf gears.
Digital Signal Multiprocessors
Digital signal processors are also called as DSP’s, these processors are used to encode and decode the videos or to convert the D/A (digital to analog) &A/D (analog to digital). They need a microprocessor that is excellent in mathematical calculations. The chips of this processor are employed in RADAR, home theaters, SONAR, audio gears, TV set top boxes and Mobile phones
There are many companies like Intel, Motorola, DEC (Digital Equipment Corporation ), TI (Texas Instruments) associated with many microprocessors such as 8085 microprocessors, ASIC, CISM, RISC, DSPs and 8086 microprocessors like Intel
Advantages and Disadvantages of Microprocessors
The advantages of microprocessors are
The processing speed is high
Intelligence has been brought to systems
Flexible.
Compact size.
Easy maintenance
Complex mathematics
Some of the disadvantages of microprocessor are it might get overheated and the limitation of the microprocessor imposes on size of data.
The applications of the microprocessors mainly involve in controllers in home appliances, wireless communication equipments, office publication and automation, consumer electronic goods, calculators, accounting system, video games, industrial controllers and data acquisition systems
APPLICATIONS OF MICROPROCESSOR
This is all about types and evolution of microprocessor.The availability of microprocessor with low power, low cost, small weight and computing capability make it useful in various applications. In present days, a microprocessor based systems are used in automatic testing product, traffic signal control systems, instructions, speed control of motors, , etc. Furthermore, any doubts regarding this article or electronic and electrical projects, please give your comments in the comment section box.Here is a question for you, which stack is used in 8085 microprocessor?
The internal structure of a microprocessor is shown below.
Earlier microprocessors made use of Von Neumann architecture where the data and instructions (programs) are stored in the same memory. Even though this architecture is simple, there are many draw backs. One of the major drawbacks is that instruction and data cannot be accessed at the same time as they share a single data bus. This often degrades the overall performance of the device. Later, Harvard architecture is introduced which makes use of separate program and data memories with separate buses so that both data and instructions can be accessed at the same time. Later Modified Harvard Architecture is developed in which the program memory is accessed as if it were data memory.
There are three basic characteristics used to differentiate microprocessors. They are instruction set, bandwidth and clock speed. Instruction set is related to programming of the microprocessor which mainly consists of instructions that a microprocessor can execute. Bandwidth indicates maximum number of bits processed in a single instruction. Clock speed gives no. of instructions a processor can execute per second. Usually clock speed is in MHz (Mega Hertz) or GHz (Giga Hertz). Generally the characteristics bandwidth and clock speed are looked together. The higher the values of both these characteristics, the more powerful the processor is.
Instruction set or instruction set architecture (ISA) also plays an important role in the design and functioning of a processor. Microprocessors are classified as either CISC (Complex Instruction Set Computer) or RISC (Reduced Instruction Set Computer).
CISC architecture consists of full set of instructions that are complex, larger, have more computational power and so on. A single CISC instruction can be used to execute several low-level operations, multi-step operations and multiple addressing modes. The execution time of these instructions is long. Intel’s X86 is an example of CISC architecture.
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