Harvard structure and von noriman Structure

Harvard Structure

The Harvard structure isSeparate storage structure of program instruction storage and data storage. The central processor first reads the content of the program instruction in the program instruction memory, decodes the content, obtains the data address, reads the data in the corresponding data storage, and performs the next operation (usually execution ). The program instruction storage and data storage are separated, so that the instruction and data have different data widths.

The Harvard structure microprocessor usually has a high execution efficiency. The program commands and data commands are organized and stored separately. The next command can be read in advance during execution.

At present, there are a lot of central processors and microcontroller using Harvard structure, except for the above-mentioned PIC chips of the microchip company, there are also the mc68 series of Motorola, Z8 series of zilog, AVR series of ATMEL, and arm10, arm11 of Amou.

The Harvard structure refers to an independent architecture of programs and data spaces. It aims to reduce the memory access bottleneck during program running.

For example, when a command takes two operands at the same time, during pipeline processing, there is also a finger fetch operation. If the program and data are accessed through a bus, the fetch and fetch operations will conflict, this is very unfavorable for the execution efficiency of large computation cycles.

The Harvard structure can basically solve the conflict between the fetch and the fetch.

　　Feng. Noriman structure (Princeton Architecture)

   The main contribution of von noriman is to propose and implement the concept of "Storage program. Since commands and data are both binary codes, and the address of commands and operands are closely related, it is natural to select this structure. However, such commands and data share the same bus structure, making information transmission a bottleneck that limits computer performance and affects data processing speed.

   Generally, it takes three steps to complete an instruction, namely, obtaining, decoding, and executing the instruction. From the regular relationship of the instruction stream, we can also see the difference between the Pattern Processing Method of the Von noriman structure and the Harvard structure. For example, for instructions on read/write operations on memory, commands 1 to 3 are memory and count commands. the norm structure processor, because the command and access data are to be accessed from the same bucket and transmitted through the same bus, they cannot overlap and execute, and only one is complete before the next.