Microprocessor Architectures

MICROPROCESSOR ARCHITECTURES

There are mainly three types of microprocessor architectures present.

1. Von-Neumann architecture

2. Harvard architecture

3. Analog devices Modified Harvard architecture.

1) Von-Neumann Architecture

General purpose microprocessors uses the Von-Neumann Architectures. (named after the American mathematician John Von Neumann)

1.It consists of ALU, accumulator, IO devices and common address and data bus. It also consists of a single memory which contains data and instructions, a single bus for transferring data and instructions into and out of the CPU.

2.Multiplying two numbers requires at leased three cycles, two cycles are required to transfer the two numbers into the CPU and one cycle to transfer the instruction.

3.This architecture is giving good performance when all the required tasks can be executed serially. 4.For large processing applications like DSP applications Von-Neumann architecture is not suitable as processing speed is less. Processing speed can be increased by pipelining up to certain extend which is not sufficient for DSP applications. In order to perform a single FIR filter multiply-accumulate, an instruction is fetched from the program memory, and during the same cycle, a coefficient can be fetched from the data memory. A second cycle is required to fetch the data word from data memory

2) Harvard Architecture (named for the work done at Harvard university)

1.     Data and program instructions each have separate memories and buses as shown. Program memory address and data buses for program memory and data memory address and data buses for data memory.

2.     Since the buses operate independently, program instructions and data can be fetched at the same time. Therefore improving speed over the single bus Von Neumann design.

3.     In order to perform a single FIR filter multiply-accumulate, an instruction is fetched from the program memory, and during the same cycle, a coefficient can be fetched from the data memory. A second cycle is required to fetch the data word from data memory.