16 Facts About CPU

Principal components of a CPU include the arithmetic–logic unit that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the fetching, decoding and execution by directing the coordinated operations of the ALU, registers and other components.

Hardwired into a CPU's circuitry is a set of basic operations it can perform, called an instruction set.

Actual mathematical operation for each instruction is performed by a combinational logic circuit within the CPU's processor known as the arithmetic–logic unit or ALU.

In general, a CPU executes an instruction by fetching it from memory, using its ALU to perform an operation, and then storing the result to memory.

Address generation unit, sometimes called address computation unit, is an execution unit inside the CPU that calculates addresses used by the CPU to access main memory.

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Some CPU architectures include multiple AGUs so more than one address-calculation operation can be executed simultaneously, which brings further performance improvements due to the superscalar nature of advanced CPU designs.

CPU cache is a hardware cache used by the central processing unit of a computer to reduce the average cost to access data from the main memory.

The frequency of the clock pulses determines the rate at which a CPU executes instructions and, consequently, the faster the clock, the more instructions the CPU will execute each second.

However, it carries the disadvantage that the entire CPU must wait on its slowest elements, even though some portions of it are much faster.

Therefore, as clock rate increases, so does energy consumption, causing the CPU to require more heat dissipation in the form of CPU cooling solutions.

Rather than totally removing the clock signal, some CPU designs allow certain portions of the device to be asynchronous, such as using asynchronous ALUs in conjunction with superscalar pipelining to achieve some arithmetic performance gains.

For example, if a binary CPU uses 32 bits to represent a memory address then it can directly address 2 memory locations.

Description of the basic operation of a CPU offered in the previous section describes the simplest form that a CPU can take.

Since only one instruction is executed at a time, the entire CPU must wait for that instruction to complete before proceeding to the next instruction.

Also in case of single instruction stream, multiple data stream—a case when a lot of data from the same type has to be processed—, modern processors can disable parts of the pipeline so that when a single instruction is executed many times, the CPU skips the fetch and decode phases and thus greatly increases performance on certain occasions, especially in highly monotonous program engines such as video creation software and photo processing.

When just a fraction of the CPU is superscalar, the part that is not suffers a performance penalty due to scheduling stalls.