Engineering Lecture notes and Ebook Download

There are basically two types of digital computer architectures. The first one is called Von Neumann architecture and later Harvard architecture was adopted for designing digital computers.

• It is named after the mathematician and early computer scientist John Von Neumann.
• Used in conventional processors found in PCs and Servers, and embedded systems with only control functions.
• The computer has single storage system(memory) for storing data as well as program to be executed.
• Processor needs two clock cycles to complete an instruction.Pipelining the instructions is not possible with this architecture.
• In the first clock cycle the processor gets the instruction from memory and decodes it. In the next clock cycle the required data is taken from memory. For each instruction this cycle repeats and hence needs two cycles to complete an instruction.
• The code is executed serially and takes more clock cycles.
• There is no exclusive Multiplier.
• Absence of Barrel Shifte.
• The programs can be optimized in lesser size.

Harvard Architecture:

• The name is originated from "Harvard Mark I" a relay based old computer.
• Used in DSPs and other processors found in latest embedded systems and Mobile communication systems, audio, speech, image processing systems.
• The computer has two separate memories for storing data and program.
• Processor can complete an instruction in one cycle if appropriate pipelining strategies are implemented.
• In the first stage of pipeline the instruction to be executed can be taken from program memory.In the second stage of pipeline data is taken from the data memory using the decoded instruction or address. 
• The code is executed in parallel.
• It has MAC (Multiply Accumulate).
• Barrel Shifter help in shifting and rotating operations of the data.
• 
  The program tend to grow big in size.