Microprocessors are at the core of personal computers, laptops, mobile phones and complex military and space systems. A microprocessor is usually a silicon chip that contains millions of transistors and other components that process millions of instructions per second. Integrated with memory chips and other special purpose chips, and directed by software, microprocessors process data and operator instructions.
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A microprocessor performs three basic steps: First, it fetches an instruction from memory; second, it uses decoding circuitry to determine what the instruction means; and third, it executes the instruction. Microprocessors are manufactured in two stages: first, a prototype is designed, thoroughly tested and revised. The chip then goes into large-scale production for integration into computers and other products.
General Purpose Processors
General purpose processors are designed for personal computers, laptops, mobile devices and large central servers. Several companies make general purpose processors, including Intel, IBM and Motorola. Companies generally come out with faster and more complex chips every two to three years. Intel is the recognized industry leader in this space. From the earlier Pentium and Centrino microprocessors to the Core 2 and Atom chips for desktop and mobile computers and the high-end Itanium and Xeon processors for server applications, Intel is generally regarded as the company that sets the benchmark for others to follow. The PowerPC microprocessors were co-developed by Motorola, Apple and IBM originally for Apple's Macintosh computers, but Apple switched to Intel chips in 2006. Apple uses other processors as well. For example, the iPad 2, introduced in March 2011, uses the Cortex-A5 processor designed for mobile computing by computer manufacturer ARM.
Microcontrollers are designed for industrial control applications, where ease of use and versatility rather than speed are the main requirements. They interface with sensors and other devices in applications ranging from on-board computers in cars to lighting systems and renewable energy control systems. Input/output and memory functions are often embedded along with the core processing functions on one chip. In addition to Intel, Freescale, Micron and Texas Instruments are major manufacturers of microcontrollers.
Digital Signal Processors
Digital signal processors are used in digital signal processing applications that require fast data sampling and complex math operations. They complement general purpose processors, not replace them. A digital signal processor chip generally includes a memory device, arithmetic logic device, controller and a data bus for transmitting data between the respective components. It also typically includes a multiply and accumulate unit that multiplies two or more data items together and adds the product to a value already stored in an accumulator. Texas Instruments, with its C6000, Integra and DaVinci processors, is one of the main players in the digital signal processing space.
Consideration: Classification by Hardware
Microprocessors may also be classified by their hardware architecture. The two basic types of hardware are CISC, or complex instruction set computer, and RISC, or reduced instruction set computer. CISC processors can perform complex functions with one instruction while RISC chips usually need multiple instructions. The Intel Pentium and Atom chips are based on the CISC architecture, while PowerPC and ARM's Cortex chips are RISC systems.