Computer Organization


 Central Processing Unit

The main unit inside the computer is the CPU. This unit is responsible for all events inside the computer. It controls all internal and external devices, performs arithmetic and logic operations. The CPU (Central Processing Unit) is the device that interprets and executes instructions


Central Processing Unit. The “brain” of the computer. It executes commands which, eventually, we see as a response to our input. Without the CPU, the computer is nothing


The Central Processing Unit (CPU) is responsible for interpreting and executing most of the commands from the computer’s hardware and software.

The CPU could be considered the “brains” of the computer.



Types of processor

There are about five different types of processors:

  • · CISC (Complex Instruction Set Computer). A classic CISC will have all instructions built into ROM’ed microcode and that takes several clock cycles to execute. They have up to two thirds unused instructions by standard processors. Because of their complexity, they require 4x the number of transistors to do the same processing as RISC. They generate more heat, require more power, and tend to be slower than RISC at the same clock speed.
  • · RISC (Reduced Instruction Set Computer). A classic RISC hard-wires every instruction and only has instructions typically used by compilers. Also more complex instructions (like “divide”) are split into at least two opcodes. Most of the time, programs converted from CISC to RISC will grow by about 33%. Nevertheless, they are still faster, cooler and cheaper to make than equivalent CISC.
  • · Microcontroller. This is a specialized microprocessor that does specialized operations. For example, most calculators or alarm systems use microcontrollers.
  • · Vector Processor. These are very fast processors that parallelize processing so that many actions can be accomplished at the same time. The use of these processors have diminished with the introduction of more powerful RISC/CISC processors.
  • · Bit Slice. These are archaic, linkable processors. Each processor would work on a certain number of bits (e.g. a 4-bit processor). With the addition of each processor, the computation word gets bigger (e.g. 5 4-bit processors can work with a 20-bit word).


Speed of Processer:

had 20-50 thousand transistors). These processors were considered “state of the art”. However, if you think about the sheer speed processing we can do now, these were plain, dog slow. For example, the Pentium/100 is easily 200x faster than the first IBM PC. That means that the Pentium processor can run the same software as the first IBM PC but will be blazingly faster. The latest processor (Pentium Pro) has 5.5 million transistors for the CPU alone.









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