As it goes with all technology, the complexity, size, construction and general form of the device modifies over time. These changes form the evolution of technology, its increased use and application for what have become everyday necessities. One such device, the personal computer, has received much of the attention in the past 40 years of the technological evolution. From its early days as a printing programmable calculator to the explosion of home-used desktops in the 90s, personal computers have transformed our lives by providing access to information and tools that previous generations would have never thought possible.

The personal computer would go nowhere if it weren’t for the CPU. The Central Processing Unit, or microprocessor, or brains of the computer carries out a sequence of stored instructions of a program by performing the basic arithmetical, logical, and input/output operations of the system. This operation is formed by the fetch-execute cycle which includes: fetch an instruction, decode the instruction, fetch any data referred to by the instruction, execute the instruction and store any new data created by the instruction (writeback).

The CPU first fetches and instruction from the program via the computer’s memory (e.g., ROM: Read Only Memory or RAM: Random Access Memory). The CPU keeps track of its position in the program by utilizing a program counter or Instruction Pointer (IP). When an instruction is fetched, the IP moves to the next instruction in the cue.

When the CPU receives its instruction, the information must be decoded by the Assembler. The Assembler takes the information (which is in assembly language) and assembles it to op code for the CPU to process.

In the next step, data is fetched pertaining to the instruction that was given to the CPU. This data is copied from memory to the CPU itself in storage known as register.

Execution of the instruction may now proceed. The CPU will perform Arithmetic Logic Unit (ALU) on the data from the instruction, make a decision about the data held in the register or jump to different addresses (change of the Instruction Pointer) in the program for the next instruction in cue, or simply move data from one storage point to another. If an error occurs in this process, consult a local computer repair expert.

Writeback is the final operation where the CPU overwrites any old data to an address in memory with any new values created by the instruction.

CPUs typically run at a speed of 2.5 GHz – 3.1 GHz (on personal computers) meaning 2.5 – 3.1 billion instructions can be processed every second; although CPU manufacturer AMD has recently released a chip that clocked a speed of 8.49 GHz. This is quite impressive when one considers the evolution of the personal computer over the past 40 years.

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