Processors are now being built with even faster ratings. With all other parameters being equal (although they never are) a CPU operating at 500 MHz can process data five times as fast as one operating at 100 MHz
Types of Processors
CISC ProcessorsOne of the earlier goals of CPU designers was to provide more and more instructions in the instruction set of a CPU, to ensure that the CPU directly supports more features, making it easier to translate high level language programs to machine language, and to ensure that the machine language programs run more effectively. Of course every additional instruction in the instruction set of a CPU requires the necessary hardware circuitry to handle that instruction, adding more complexity to the CPU’s hardware circuitry. Another goal of CPU designers was to optimize the usage of expensive memory. To achieve this, the designers tried to pack more instruction in memory, by introduction the concept of variable-length instructions such as half word, one and half word, etc.
For example and operand in an immediate instruction needs fewer bits, and can be designed as half word instruction. Additionally, CPU,s were designed to support a variety of addressing modes .CPUs with large instruction set, variable length instructions and a variety of addressing modes are said to employ CISC(Complex instruction set computer) architectures, Since CISC processors posses so many processing features, they make the job of machine language programmers easier. However they are complex and expensive to produce. Most personal computers of today use CISC processors.