Processors

A processor is a circuit responsible for executing instructions and performing calculations.

The most common type of processor is the microprocessor, which contains all of the circuits needed to perform the functions of a computer including arithmetic, logic, and data processing.

Microprocessors are integrated circuits with a large number of MOSFET transistors that are used to store and operate on binary voltage signals. The state of a transistor (off/on) corresponds with a zero (0) or one (1) binary value.

Processors function by executing binary machine code. While pure machine code would be incredibly difficult for a human to read, it can be understood much more easily in the form of assembly.

Since processors process machine code and assembly is human-readable machine code, it stands that learning assembly is one of the best ways to learn about processors.

There are two primary parts of a processor: an arithmetic and logic unit (ALU) and a control unit (CU).

Arithmetic and Logic Unit (ALU)

The Arithmetic and Logic Unit (ALU) is a fundamental component of a processor that performs arithmetic and logic operations.

It is responsible for performing computation and manipulation of data within the CPU. The ALU performs operations such as addition, subtraction, AND, OR, and NOT operations.

The ALU takes input from the processor’s registers, performs the specified operation, and then stores the result back in the registers. The ALU is a critical part of the CPU and is used in almost all computational tasks performed by the processor.

Control Unit (CU)

The Control Unit (CU), also known as the ‘Control Logic’ section, is a component of a processor that manages the execution of machine code instructions. It is responsible for fetching the instructions from memory, decoding them, and executing them by coordinating the activities of other parts of the CPU.

The Control Unit works in conjunction with the Arithmetic and Logic Unit (ALU) and other components of the CPU to execute program instructions. It uses signals to control the flow of data between the CPU, memory, and other peripherals.

The Control Unit is responsible for controlling the overall operation of the CPU, ensuring that instructions are executed in the correct sequence and coordinating the activities of other components to carry out those instructions.

Instruction Cycle

A processor uses the Arithmetic and Logic Unit (ALU) and Control Unit (CU) in conjunction to perform its operations and functions. Here’s a basic overview of how they work together:

  1. Fetch: The Control Unit fetches an instruction from memory. This instruction specifies the operation to be performed.
  2. Decode: The Control Unit decodes the instruction, determining which operation needs to be performed and which operands (data) are involved.
  3. Execute: The Control Unit coordinates with the ALU to execute the instruction. The ALU performs the specified arithmetic or logic operation on the operands.
  4. Store: If the operation produces a result, the result is written back to a register or memory location as specified by the instruction.
  5. Repeat: The process continues, with the Control Unit fetching the next instruction and repeating the cycle.

The Control Unit manages the flow of instructions and data within the processor, ensuring that instructions are executed in the correct sequence and that the ALU performs the correct operations. The ALU is responsible for actually performing the arithmetic and logic operations specified by the instructions.

Together, the ALU and CU form the core of the CPU, executing program instructions and performing the computations required for the operation of the computer.

Processor vs. Microprocessor vs. CPU

The terms “processor,” “microprocessor,” and “CPU” (Central Processing Unit) are often used interchangeably, but they have slightly different meanings:

  • Processor: The term “processor” generally refers to any device that processes information. In the context of computers, it often refers to the CPU or the main processing unit of a computer.
  • Microprocessor: A microprocessor is a type of processor that contains the CPU on a single integrated circuit (IC) or chip. Microprocessors are used in most modern computers and electronic devices.
  • CPU (Central Processing Unit): The CPU is the primary component of a computer that performs most of the processing inside the computer. It executes instructions, performs calculations, and manages the flow of data within the computer. The CPU often includes the ALU (Arithmetic and Logic Unit) and the Control Unit.

In summary, a microprocessor is a type of processor, and the CPU is a specific component of a computer or microprocessor. However, in common usage, these terms are often used interchangeably to refer to the main processing unit of a computer.

Common Processors in Computers

The CPU is the most important processor in any computer, but it isn’t the only one. Common processors other than the CPU include:

  • Graphics Processing Unit (GPU): A GPU is a specialized processors designed to handle graphics and image processing tasks. They are commonly used in video games, graphic design, and other applications requiring intensive visual processing.
  • Digital Signal Processor (DSP): DSPs are processors optimized for processing digital signals, such as audio, video, and sensor data. They are commonly used in telecommunications, audio processing, and digital image processing.
  • Network Processor: A network processor is a specialized processor designed to handle networking tasks, such as routing, switching, and packet processing. They are commonly used in routers, switches, and other networking devices.
  • Co-processor: The co-processor is a secondary processor designed to assist the main CPU in specific tasks, such as floating-point calculations or encryption. They can improve performance and efficiency for certain types of computations.
  • Accelerator: An accelerator is a processor designed to accelerate specific types of computations, such as machine learning, artificial intelligence, or scientific simulations. They are often used in conjunction with CPUs and GPUs to improve performance for these tasks.

What is a Processor?

A processor is a circuit that contains a variety of electronic components, including large numbers of transistors.

The vast majority of processors today are found in the form of an integrated circuit. This means that all of the circuitry is found in a single self-packaged chip.

Modern fabrication methods allow for many millions of MOSFET transistors to be located on the same chip. The transistors can hold an ‘on’ or an ‘off’ state. An ‘on’ state corresponds with a binary value of 1, while an ‘off’ state corresponds with a binary value of ‘0’.

The fact that a transistor can hold a binary state is the foundation of modern computing.

Using transistors, we can easily create circuits that perform simple math (like adding two numbers together) and logic gates like AND, OR, and NOT.

Long before modern computers existed, scientists and mathematicians had already developed Boolean algebra. Boolean algebra is a system of logic based on binary mathematics – in other words, it allows any binary computer to perform logical operations like AND, OR, and NOT.

These operations can be combined, along with mathematical operations, to perform all of the complex instructions required by a modern processor.