The three steps of running a program in a computer are: 1. Instruction fetching stage, fetching relevant instructions from the instruction cache and sending the instructions to the instruction register; 2. Decoding stage, sending the instructions to the instruction decoding Decoding in the device, the instruction decoder sends a control signal, and the program counter adds 1 to point to the next instruction; 3. In the execution phase, the data is loaded into the register, and the operation status is recorded. If there is a carry or overflow, it is recorded in the status register, and then The operation results are sent through the on-chip bus.
The operating environment of this tutorial: Windows 10 system, DELL G3 computer.
Fetching instructions, decoding, and executing
The detailed operations of each step are as follows
Instruction fetching stage:
1. Fetch the relevant instructions from the instruction cache
2. Send the instructions to the instruction register
Analysis instructions:
1. Send the instruction to the instruction decoder for decoding
2. The instruction decoder sends a control signal, and at the same time, the program counter increases by 1 and points downward. An instruction
points to the instruction:
1. Load data into register
2. ALU processes data
3. Record The operation status, if there is a carry or overflow, is recorded in the status register
4. Send the operation result through the on-chip bus
Expand knowledge
CPU pipeline design
The above process is the general operation of the instruction execution process. The above demonstration basically covers each step of the instruction execution process.
There is a problem in the instruction execution process. When instructions need to be fetched and analyzed, the controller is mainly responsible for the work. When the instructions are executed, the arithmetic unit is mainly responsible for the work. That is to say, the arithmetic unit and the controller cannot work at the same time, resulting in low comprehensive utilization of the CPU. Therefore, it is necessary to improve the instruction execution process to improve the comprehensive utilization of the CPU. The improvement method is pipeline design.
The CPU assembly line design is similar to a factory assembly line. The factory assembly line allows multiple products to be processed at the same time. At the same time, different products are in different stages of processing.
When pipeline design is not applied, computer instructions are executed serially:
When pipeline design is used, computer instructions are executed in parallel as shown below Executed:
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