Computer system architecture

Computer architecture means design or construction of a computer. A computer sustem may be organized in different ways. Some computer systems have single processor and other have multiprocessors. So computer systems categorized in these ways.

1.      Single Processor Systems

2.      Multiprocessor Systems

3.      Clustered Systems

Single processor

Some computers use only one processor such as microcomputers. On a single processor system, there is only one CPU that perform all the activities in the computer system, However, most of these systems have  other special purpose processors, such as I/O Processor that move data rapidly among different components of the computer system. These processors execute only a limited system programs and do not run the user program. So we define single processor systems as “ A system that has only one general purpose CPU, is considered as single processor system.

Multiprocessor systems

Some systems have two or more processors. These systems are also known as parallel systems or tightly coupled systems. Mostly the processors of these systems share the common system bus (electronic path) memory and peripheral (input/output) devices. These systems are fast in data processing and have capability to execute more than one program simultaneously on different processors. This type of processing is known as multiprogramming or multiprocessing. Multiple processors further divided in two types.

                                     i.            Asymmetric Multiprocessing Systems (AMS)

                                   ii.            Symmetric Multiprocessing Systems (SYS)

Asymmetric multiprocessing systems

The multiprocessing system, in which each processor is assigned a specific task, is known as Asymmetric Multiprocessing Systems. In this system there exists master slave relationship like one processor defined as master and others are slave. The master processor controls the system and other processor executes predefined tasks. The master processor also defined the task of slave processors.      

Symmetric multiprocessing system

The multiprocessing system in each processor performs all types of task within the operating system. All processors are peers and no master slave relationship exits. In SMP systems many programs can run simultaneously. But I/O must control to ensure that data reach the appropriate processor because all the processor shares the same memory.

Clustered systems

Clustered systems are another form of multiprocessor system. This system also contains multiple processors but it differs from multiprocessor system. The clustered system is composed of multiple individual systems that connected together. In clustered system, also individual systems or computers share the same storage and liked to gather via local area network. A special type of software is known as cluster to control the node the systems.

Other form of clustered system includes parallel clusters and clustering over a wide area network. In parallel cluster multiple hosts can access the same data on the shared storage. So many operating systems provide this facility but some special software are also designed to run on a parallel cluster to share data.