CPU is the brain of a computer system. It performs all major calculations and comparisons, and also activates and controls the operations of other units of the computer system. Hence, no other single components of a computer determines its overall performance as much as its CPU. In order to evalute a computer's capabilities quickly, it is important to know how CPUs are internally structured, how different CPUs differ from each other, and how to evaluate CPU speed. These and other related concepts are described below.
Control unit (CU) and arithmetic logic unit (ALU) of a computer system are together known as the central Processing Unit (CPU). It is the brain of a computer system. In a human body, the brain takes all major decisions and other parts of the body function as directed by the brain. Similarly, in a computer system, the CPU performs all major calculations and comparisons, and also activates and controls the operations of other units of the computer system.
The CPU in modern computers is the embodiment of the "mill" in Babbage's difference engine. The term central processing unit originated way back in the mists of computer time when a single massive cabinet contained the circuitry required to interpret machine level program instructions and perform operations on the data supplied. The central processing unit also completed all processing for any attached peripheral devices. Peripherals included printers, card readers, and early storage devices such as drum and disk drives. Modern peripheral devices have a significant amount of processing power themselves and off-load some processing tasks from the CPU. This frees the CPU up from input/output tasks so that its power is applied to the primary task at hand.
Early computers only had one CPU and could only perform one task at a time. We retain the term CPU today, but now it refers to the processor package on a typical motherboard. Figure 1 displays a standard Intel processor package.
There is really nothing to see here other than the processor package itself. The processor package is a chip containing the processor(s) sealed inside a metal container and mounted on a small printed circuit (PC) board. The package is simply dropped into place in the CPU socket on a motherboard and secured with a locking lever arrangement. A CPU cooler attaches to the processor package. There are several different physical sockets with specific numbers of contacts, so getting the correct package to fit the motherboard socket is essential if you build your own computers.
A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions. The term has been used in the computer industry at least since the early 1960s. Traditionally, the term “CPU” refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry. The form, design and implementation of CPUs have changed over the course of their history, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic logic unit (ALU) 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 fetches instructions from memory and “executes” them by directing the coordinated operations of the ALU, registers and other components.
Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip. An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously calledmicrocontrollers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called “cores”; in that context, single chips are sometimes referred to as “sockets”. Array processors or vector processors have multiple processors that operate in parallel, with no unit considered central.