Von Neumann System
Features of Von Neumann's computer architecture:
1. The computer is composed of five major components: memory + arithmetic unit + controller + input device + output device
2. Instructions and data are stored in the memory in the same position and can be accessed by address
3. Instructions and data are expressed in binary
4. Instructions are represented by opcodes It is composed of an address code. The opcode indicates the nature of the operation, and the address code indicates the location of the operand in the memory.
5. Instructions are stored in order in the memory. Usually, instructions are executed sequentially. In special cases, the order of operations can be changed according to the operation results or specified conditions.
6. Take CPU as the core and memory as the center.
Five major components
- Storage body
Storage body-containing-storage unit-containing-storage element (0/1)
can be imagined as: building-containing-room-containing-bed (unoccupied/occupied)
The storage unit: storing a string of binary code
stored words: a combination storing unit binary code
stored word length: the storage unit number of binary code
of each memory cell is assigned a number of address by address search
MAR: Memory address register, which reflects the number of memory cells.
MDR: Memory data register, reflecting the storage word length.
Set MAR=4 bits, MDR=8 bits, then the number of storage units is 16, and the storage word length is 8
2. Operator
ACC: accumulator
ALU: arithmetic logic unit
MQ: multiplier register
| ACC | SQM | X | |
|---|---|---|---|
| addition | Store the summand and sum | null | Store addend |
| Subtraction | Store the subtracted number and difference | null | Store minus |
| multiplication | Store the product high | Store multiplier and product status | Store the multiplicand |
| division | Store dividend and remainder | Depositor | Store divisor |
- Controller
PC: program computer (program computer)
IR: instruction register (instruction register)
CU: control unit (control unit) The
PC sends the instruction to the IR by taking the address, and the CU executes the command in the IR.
The controller completes an instruction in three steps: fetch the instruction, analyze the instruction, and execute the instruction.
Instruction fetching: Through address fetching, the PC stores the address of the current instruction to be executed and the PC has a counting function (PC)+1 → PC.
Analysis instructions: IR stores the instructions currently to be executed.
Execution instructions: CU is the core
4.5.
Input and output devices are omitted
The process by which a computer completes an instruction
1 2 3 4 Completed the instruction fetch
5 Completed the analysis instruction, put the instruction into the CU, so that the computer knows what to do
6 7 8 9 Completed the execution instruction, fetched the number
The storage instruction only needs to reverse the arrows of 8 and 9 to complete the storage.