Answer to Question #324599 in Computer Networks for Mimi

Question

Using an appropriate diagram:

1. Apply the fetch, decode & execute machine cycle to explain

pipelining and parallelism in the context of computing

Answer 1

The fetch cycle is the point in which the CPU’s control unit will read the next instruction to perform from memory. Since everything in a computer is in the form of data in some way, the actual instructions it has to follow also have to come from somewhere. The fetch cycle is ensuring that once an instruction is executed, the next instruction is on its way into the pipeline. Modern CPUs will rarely have just one instruction being done at a time per core, but will do their best to saturate their pipelines with as many stages of as many instructions as possible.

The execute cycle is actually any cycle in which the actual procedures defined by the opcode are being carried out. This would include reading data from memory or another register, performing some math or logical operation, and outputting the result. While fetch is about figuring out what to do next, the execute is about actually doing what it found out.

Below is the procedure how the execution is done.

1. The CPU fetches the instructions one at a time from the main memory into the registers. One register is the program counter (pc). ...
2. The CPU decodes the instruction.
3. The CPU executes the instruction.
4. Repeat until there are no more instructions.