The important contribution of von N

The important contribution of von Neumann is to propose and implement the concept of "memory program". Since instructions and data are binary codes, and the address of instructions and operands are closely related, it is natural to choose this structure at the beginning. However, this kind of instruction and data share the same bus structure, which makes the transmission of information flow become the bottleneck of computer performance, and affects the improvement of data processing speed.In a typical case, it takes three steps to complete an instruction: fetching instruction, decoding instruction and executing instruction. From the timing relationship of instruction flow, we can also see the difference between the von Neumann structure and the Harvard structure. For example, the simplest instruction to read and write to the memory is from instruction 1 to instruction 3. For the von Neumann structure processor, since the instructions to be fetched and the data to be accessed from the same storage space and transmitted through the same bus, they cannot be executed in an overlapping manner. Only one instruction is completed before the next instruction.