Central Processing Unit or CPU
A general purpose computer has four main sections: the arithmetic and logic unit (ALU), the control unit, the memory, and the input and output devices (collectively termed I/O). These parts are interconnected by busses, often made of groups of wires. The control unit, ALU, registers, and basic I/O (and often other hardware closely linked with these) is collectively known as a Central Processing Unit (CPU).
Primitive CPUs were comprised of many separate components but since the mid-1970s CPUs have typically been constructed on a single integrated circuit called a microprocessor. CPU plays a role analogous to the brain in the computer.
The CPU can be a single chip or a series of chips that perform arithmetic and logical calculations and that time and control the operations of the other elements of the system. It was the contribution of the miniaturization and integration techniques that made possible the development of the microprocessor. A Microprocessor is a CPU chip that incorporates additional circuitry and memory. Typical CPU chips and microprocessors are composed of four functional sections:
- Arithmetic/logic unit (ALU): gives the chip its calculating ability and permits arithmetical and logical operations
- Registers: The registers are temporary storage areas that hold data, keep track of instructions and hold the location and results of these operations.
- Control section: The control section times and regulates the operations of the entire computer system; its instruction decoder reads the patterns of data in a designated register and tmnslates the pattern into an activity, such as adding or comparing; and its interrupt unit indicates the order in which individual operations use the CPU and regulates the amount of CPU time that each operation may consume.
- An internal bus: It’s a network of communication lines that connect the internal elements of the processor and also leads to external connectors that link the processor to the other elements of the computer system.
The CPU Buses are of three types:
- Control bus consisting of a line that senses input signals and another line that generates control signals from within the CPU
- Address bus that is one-way line from the processor that handles the localion of data in memory addresses
- Database, which is a two-way transfer line that both reads data from memory and writes new data into memory.
Dual Core and Quad Core
Development of multi-core processors is one of the latest trends in the computer industry, because single core processors rapidly reach the physical limits of possible complexity and speed. A multi-core microprocessor is one that combines two or more independent processors into a single package, generally in a single integrated circuit (lC). A Dual Core is device that contains two independent microprocessors and a Quad-core device contains four microprocessors. Multi-core processor has enhanced performance, reduced power consumption, and more efficient simultaneous processing of multiple tasks.
A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are to cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.