The Central Processing Unit (CPU) is one of the most important components of a computer. It is known by several names such as central processor, main processor, microprocessor, or just processor.
The computer processor is a small chip (logic circuitry) that resides in computers and other electronic devices.
Its basic function is to receive and process basic instructions that drive a computer. It is among the most important components inside the computer.
It processes information and interfaces with other system elements to retrieve data to be processed. The speed of the processor is a major factor in determining the performance of the PC.
Generally, the Central Processing Unit Performs the Following Functions:
- Decodes and executes instructions obtained from software programs.
- Performs arithmetic calculations.
- Controls and supports the timing of each operation.
What is Meant by a Computer Processor?
A processor is an integrated electronic circuit that performs the calculations that run a computer. The processor is a flat plate of silicon made up of millions of transistors. The transistors are etched onto the plate in a huge computer logic framework.
Ceramic material is used to cover the microcircuit. It protects and also conducts heat away to the heat sink. This protective ceramic cover has print information on the processor type and other useful information.
How the Computer Processor Operates
The basic operation of most computer processors, regardless of their physical form, is to execute a sequence of stored instructions called a program. The instructions to be executed are kept in computer memory.
Nearly all CPUs follow the fetch, decode and execute steps in their operation, which are collectively known as the instruction cycle.
After the execution of an instruction, the entire process repeats. The next instruction cycle normally fetches the next-in-sequence instruction because of the incremented value in the program counter.
If a jump instruction was executed, the program counter will be modified to contain the address of the instruction that was jumped to and program execution continues normally. In more complex CPUs, multiple instructions can be fetched, decoded, and executed simultaneously.
Fetch Cycle
The first step a processor does is to fetch. It involves retrieving an instruction (which is represented by a number or sequence of numbers) from program memory.
The program counter (PC) determines the instruction’s location (address) in program memory.
This counter stores a number that identifies the address of the next instruction to be fetched.
After an instruction is fetched, the PC is incremented by the length of the instruction so that it will contain the address of the next instruction in the sequence.
Most often the instruction is retrieved from relatively slow memory. This action causes the CPU to stall while waiting for the instruction to be returned.
This issue is largely addressed in modern processors by the use of cache memory and pipeline architectures.
Decode Cycle
The instruction fetched by the central processing unit from memory determines what the processor will do.
In the decode step, performed by the circuitry known as the instruction decoder, the instruction is converted into signals that control other parts of the CPU.
The CPU’s instruction set architecture (ISA) defines how the instruction is to be interpreted. Often, one group of bits (that is, a “field”) within the instruction, called the opcode, indicates which operation is to be performed.
The remaining fields usually provide supplemental information required for the operation, such as the operands. Those operands may be specified as a constant value (called an immediate value), or as the location of a value that may be a processor register or a memory address, as determined by some addressing mode.
Execute Cycle
After the fetch and decode steps, the execute step is performed. Depending on the CPU architecture, this may consist of a single action or a sequence of actions.
During each action, various parts of the central processing unit are electrically connected. This enables them to perform all or part of the desired operation and then the action is completed. This is usually in response to a clock pulse.
Results are written to an internal CPU register for quick access by subsequent instructions. In other cases, results may be written to slower, but less expensive and higher capacity main memory.
Components of the Central Processing Unit
In the CPU, there are two primary components namely the Arithmetic Logic Unit and Control Unit.
CU (Control Unit)
The control unit controls all the operations taking part in the computer. However, it does not carry out any actual data processing operations.
- It controls the transfer of data and instructions among other units of the computer.
- The control unit manages and coordinates all the units of the computer.
- It obtains the instructions from the memory, interprets them, and directs the operation of the computer.
- It communicates with Input / Output devices for the transfer of data or results from storage.
ALU (Arithmetic Logic Unit)
The Arithmetic Logic Unit consists of two sections namely the Arithmetic unit and Logic unit.
Arithmetic Unit
The arithmetic section performs arithmetic operations like addition, subtraction, multiplication, and division. All complex operations are done by making repetitive use of the above operations.
Logic Unit
The function of the logic unit is to perform logic operations such as comparing, selecting, matching, and merging data.
What Factors Affect Central Processing Unit Performance?
Modern-day processors are extremely fast though their performance can be affected by several factors.
Clock Speed
Clock speed is also referred to as clock rate, PC frequency and CPU frequency. The clock speed (or clock rate) is stated in megahertz (MHz) or gigahertz (GHz).
It refers to the speed at which the processor can execute instructions. The faster the clock, the more instructions the processor can complete per second.
Most CPUs are synchronous circuits, which means they employ a clock signal to pace or control their sequential operations.
An external oscillator circuit generates the clock signal. This circuit generates a consistent number of pulses each second in the form of a periodic square wave.
This frequency of the clock pulses is the one that determines the rate at which a CPU executes instructions.
Instruction Set of the Computer Processor
This is the processor’s built-in code that tells it how to execute its tasks. It is an architectural design coded into the chip during the manufacturing process.
The processor’s architecture and instruction set determines how many cycles are needed to execute a given instruction.
Bandwidth
Bandwidth is measured in bits. It determines how much information the processor can process in one instruction. A good analogy is to compare data flow to the flow of traffic on a highway.
The clock speed is the speed limit, and bandwidth is the number of lanes on the highway. Computer processors are either 32-bit or 64-bit CPUs.
Cache Memory
Cache memory is a relatively small amount of high-performance SRAM (Static Random Access Memory) built directly into the processor. It enables the processor to access repeatedly used data directly from its onboard memory.
This is as opposed to repeatedly requesting it from the system RAM. In the early days of computing, processors were getting faster, but the memory was not. To address this problem, engineers put tiny amounts of fast memory on the processor itself.
The level 1 cache is the smallest and fastest RAM on the computer. It stores the information that a particular core of the processor is most likely to require to complete its present task.
The level 2 cache is larger, but not quite as fast. It holds the information the processor core is most likely to need to complete its next task. Level 3 is much larger but slower.
Number of Cores
A core is a processing unit within a CPU. Each core is capable of fetching, decoding and executing its instructions. The more cores a CPU has, the greater the number of instructions it can process.
Many modern CPUs are dual (two) or quad (four) core processors. This yields superior processing power compared to CPUs with a single core.
Front Side Bus (FSB) Speed
The FSB is the interface between the processor and the system memory. The FSB speed limits the rate at which data can get to the CPU.
This in turn limits the rate at which the CPU can process that data. The CPU’s FSB speed determines the maximum speed at which it can transfer data to the rest of the system.
How to Install a New Central Processing Unit
Installing a new CPU is becoming less common but it is not a thing out of the normal. In many cases, installing additional memory is a more effective upgrade than installing a new CPU.
However, there are times you will find yourself in need of installing a new processor. If you are assembling your PC, you will install it yourself.
Before you make any purchase, determine whether the CPU can be upgraded and, if so, to what. The answer to this question lies in the motherboard.
The motherboard must have the appropriate socket, data bus; address bus, and crystal to support the new CPU.
Consult the documentation that comes with the motherboard. Ensure that a table defining the processors that can be installed is present. You can also consult the motherboard manufacturer either through the company’s Web site or via a phone call.
General Procedure for Installing a Central Processing Unit
1. Turn off the computer and unplug the power cord to the system unit.
2. Follow the appropriate ESD safety procedures. If you have no antistatic kits, just ground yourself by touching the unpainted metal of your computer or touching a metal water tap.
3. Remove the cover of the computer.
4. Locate the CPU to be removed. It will always be under the metal heat sink with a cooling fan attached.
5. Remove any cables, components or drives that might hinder a smooth operation. Note how everything is connected.
6. Unplug the cooler from the motherboard.
7. Detach the lever on the side of the CPU socket cover to allow you to remove the CPU.
You are Almost Done on Installing a Central Processing Unit
8. Install the new computer processor, and align the chip properly. Pin 1 on the CPU must fit pin 1 in the socket. There are indicators on the CPU and socket to help you get the alignment correct. Look for a matching indicator on the corner of your CPU and the socket.
It will likely appear as a small triangle. If you don’t see any indicator, you should consult the manuals for your motherboard and CPU. If you have lined up your CPU with the socket, it should drop right into place.
9. Once the CPU is properly seated in the socket, push down the retention arm with ease (and if it’s an Intel CPU, lower the bracket first).
10. Apply the thermal paste on top of the processor. This helps conduct heat from the processor to the CPU cooler by removing any imperfections on the contact surfaces. Place the heat sink and fan.
11. Reattach the components, cables, and drives you disconnected.
12. Reconnect any peripherals (keyboard, mouse, and monitor).
13. Close your fingers and power up your computer.
Some Central Processing Unit Manufacturers / Designers
Apart from Intel’s range of processors, there are other manufacturers such as:
- Advanced Micro Devices (AMD)
- Cyrix
- Integrated Device Technology (IDT)
- Qualcomm
- NVIDIA
- IBM
- Samsung
- Motorola
- Hewlett-Packard (HP)
- Dell
- Acer
- VIA
- Marvell
- Global Foundries
- Media Tek
Each of these offers competitively priced processor chips with comparable performance to Intel processors.
Conclusion
The form, design, and implementation of CPUs will indeed keep changing over time, but their basic operation remains almost unchanged. Hope you have enjoyed this article.
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