Types of Processor

A multi-purpose machine is a machine that can only carry out one task at once. A program can must be loaded into the machine, decoded, processed and executed before the next one can be fetched.

It is called multipurpose because it can do lots of different tasks, just only one task can be carried out at a time.

An example of this is the John Von Neumann Architecture.  It was designed in the 1940s and follows the idea that programs and data are stored on memory and then accessed by the processor when required. This is then passed between the processor and memory unit via one bus.

Instructions and data are stored together in memory.





The Harvard Architecture is an adaption of the Von Neumann Architecture. It works in the same way but stores the data and programs separately (each connected by a separate bus) so the two can be accessed simultaneously.



Von Neumann Architecture Vs Harvard Architecture:




Modern day (Contemporary Processor Architecture) computers use a combination of both Von Neumann & Harvard Architecture:

There is one main memory for both data and instructions, but cache memory (the high speed low storage memory inside the CPU) is divided into two parts (one for instructions, one for data). Two different busses are used to collect the data and instructions. 

Some computers have multiple buses to speed up the process (two write, two read and one for instructions). 

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