Von neumann vs Harvard : Introduction to the computer architecture
Von-Neumann architecture
· This architecture model is introduced by John von Neumann in 1945. This architecture is described how a digital computer would work and a “stored-program computer”. EDVAC was the first digital computer built based on this architecture.
· This architecture contains the following components.
o ALU unit for executing instructions
o Control unit contains program counters and registers.
o Memory for store data and instructions.
o Mass storage
o Input / output storages
· In von Neumann architecture is using a common bus to fetch data and instruction from ram. So CPU cant performs data and instruction actions at the same time. This is known as a von Neumann bottleneck.
Harvard architecture
· Harvard architecture has different buses for fetching data and instruction. It solves bottleneck situation von Neumann architecture.
· In Harvard architecture CPU can simultaneously read-write data and instructions because of having different pathways.
· CPU can access different memory modules at the same time. Thus overall speed is high.
· In Harvard, model CPU can perform a task without fully depend on the cache memory. CPU can fetch relevant data without waiting in the queue.
· We can see Harvard architecture based chips in microcontrollers. In ATMEGA chip which we used for our hardware project is using this architecture.
How does computer execute the instruction.
The memory contains the memory modules. A module contains data and instructions. CU getting these modules one by one to the execution. When CPU gets first instruction program counter register will increasing by 1. Instruction register storing the instruction what have to execute. After performing execution result of the arithmetic operation storing under the accumulator register before saving back to the RAM.