What is Microprocessor?

Introduction to Microprocessor

microprocessor is one of the most central parts of a modern personal computer or, in fact, any advanced computer device. It integrates the functions of a central processing unit , the portion of a computer responsible for carrying out programmed instructions, onto a single integrated circuit that couples the important thinking devices of the machine with the electrical infrastructure needed to support them. Microprocessor design is able to incorporate a tremendous amount of processing power in a very small space.Before the development of the microprocessor, there were a variety of early technologies for simulating logic functions in computing devices.


These early technologies were extremely expensive, slow, and prone to failure.The microprocessor has many functions like functions of data storage, interact with various other devices and other time related functions. But, the main function is to send and receive the data to make the function of the computer well. In this article I am going to discuss about the types and evolution of microprocessor,advantages and many more about it.

Block diagram of Microprocessor

block diagram of microprocessor-engineeringprayog.com

Evolution of microprocessor

evolution of microprocessor-engineeringprayog.com

Intel 4004

The Intel 4004 was a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. It was the first complete CPU on one chip, and also the first commercially available microprocessor. the 4001 was a ROM (read-only memory) with four lines of output the 4002 was a RAM (random access memory) with four lines of input/output the 4003 was a static shift register to be used for expanding the I/O lines, for example, for keyboard scanning or for controlling a printer. The 4004 included control functions for memory and I/O, which are not normally handled by the microprocessor.



Architecture of Intel 4004 Microprocessor


Intel 8080

In computer architecture, 8-bit integers, memory addresses, or other data units are those that are 8 bits (1 octet) wide. Also, 8-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size. 8-bit is also a generation of microcomputers in which 8-bit microprocessors were the norm.The first widely adopte Intel 8080 was the first widely adopte 8-bit microprocessor designed and manufactured by Intel and was released in April 1974,it was a complete 8-bit computer on one chip.There are 28 (256) different possible values for 8 bits.Modernized variants of these 8-bit machines are still one of the most common types of processor in embedded systems.intel 8080-engineeringprayog.com

Architecture of Intel 8080 Microprocessor

intel 8080 architecture-engineeringprayog.com

Intel 8085

The Intel 8085 is an 8-bit microprocessor introduced by Intel in 1977. It was binary-compatible with the more-famous Intel 8080 but required less supporting hardware, thus allowing simpler and less expensive microcomputer systems to be built. The 8085 had a long life as a controller. The processor has seven 8-bit registers named A, B, C, D, E, H, and L, where A is the 8-bit accumulator and the other six can be used as independent byte-registers or as three 16-bit register pairs.

intel 8085 microprocessor-engineeringprayog.com

The 8085 has extensions to support new interrupts, with three maskable vectored interrupts (RST 7.5, RST 6.5 and RST 5.5), one non-maskable interrupt (TRAP), and one externally serviced interrupt (INTR). Each of these five interrupts has a separate pin on the processor. It consists of three main sections, an arithmetic and logic unit a timing and control unit and several registers. These important sections are
described as under.


The arithmetic and logic unit, ALU performs the following arithmetic and logic
1. Addition
2. Subtraction
3. Logical AND
4. Logical OR
6. Complement (logical NOT)
7. Increment (add 1)
8. Decrement (subtract 1)
9. Left shift (add input to itself)
10. Clear (result is zero)

Timing and Control Unit

The timing and control unit is a section of the CPU. It generates timing and control signals which are necessary for the execution of instructions. It controls provides status,control and timing signals which are required for the operation of memory and I/O 2 devices. It controls the entire operation of the microprocessor and peripherals consented to it. Thus it is seen that control unit of the CPU acts as a brain of the computer.


Registers are small memories within the CPU. They are used by the microprocessor for temporary storage and manipulation of data and instructions. Data remain in the registers till they are sent to the memory or I/O devices. In a large computer the number of registers is more and hence the program requires less transfer of data to and from the memory. In small computers the number of registers is small due to the limited size of the chip. Intel 8085 microprocessor has the following registers.
1. One 8-bit accumulator (ACC) i.e. register A.
2. Six 8-bit general purpose registers. These are B, C, D, E, H and L.
3. One 16-bit program counter, PC.
4. Instruction register
5. Status register
6. Temporary register.

Pin diagram of intel 8085 microprocessor

8085 pin diagram-engineeringprayog.com

Architecture of 8085 micriprocessor

architecture of 8085 microprocessor-engineeringprayog.com


The name comes from the Greek word for “five” and is used because it’s the fifth processor in the 80×86 line. It would have been called the 80586 had a US court not ruled that you cannot trademark a number. Pentium processors are considered entry-level products that Intel rates as “two stars”,[1] meaning that they are above the low-end Atom and Celeron series, but below the faster Core i3, i5, i7, i9, and high-end Xeon series.The original Pentium branded CPUs were expected to be named 586 or i586, to follow the naming convention of prior generations (286, i386, i486). However, as the firm wanted to prevent their competitors from branding their processors with similar names (as AMD had done with their Am486), Intel filed a trademark application on the name in the United States, but was denied because a series of numbers was considered to lack trademark distinctiveness.

pantium 1-engineeringprayog.com




Pentium compatible Intel processors

Due to its prominence, the term “Pentium compatible” is often used to describe any x86 processor that supports the IA-32 instruction set and architecture. Even though they do not use the Pentium name, Intel also manufactures other processors based on the Pentium series for other markets. Most of these processors share the core design with one of the Pentium processor lines, usually differing in the amount of CPU cache, power efficiency or other features. The notable exception is the Atom line, which is an independent design.

  • Celeron, a low-end version
  • Core, the mainstream version including Core 2 and Core i7, now placed above Pentium
  • Xeon, a high-end version used in servers and workstations
  • A100 (discontinued), an ultra-mobile version of Pentium M
  • EP80579, a system-on-a-chip based on Pentium M
  • Atom, current ultra-mobile processors
  • Xeon Phi, a high-end version used in servers and workstations

Architecture of Pentium processor



How Does the µ-processor work?

The microprocessor works according to the pattern: “READ, INTERPRET & PERFORM” or  “FETCH,DECODE & EXECUTE”.The instructions are stored sequentially in the memory. then µ-processor fetches the data/instruction from its memory sheet, decodes it, and executes that instruction. This process is continued untill the µ-processor comes across an instruction to STOP. During this entire process µ-processor uses the system bus to fetch the binary instructions and data from the memory. It uses registers from the register section to store data temporarily, and it performs the computing function in the ALU section. Finally it sends out the result in binary, using the same bus-lines to output ports.

working microprocessors-engineeringprayog.com

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