THE MACHINE CYCLE
The machine cycle consist of 4 main stage which is 1. FETCH 2. DECODE 3. EXECUTE 4. STORE.
The four steps which the CPU carries out for each machine language instruction, fetch, decode, execute, and store. These steps are performed by the control unit and may be fixed in the logic of the CPU or may be programmed as microcode which is itself usually fixed (in ROM) but may be (partially) modifiable (stored in RAM).
Instruction cycle: In instruction cycle CPU takes two steps--
1. Fetching: Before the CPU can execute an instruction, the control unit must retrieve or fetch a command or data from the computer's memory.
2. Decoding: Before a command can be executed, the control unit must decode the command into instruction set.
Execution cycle: In execution cycle CPU also takes two steps--
3. Executing: When the command is executed, the CPU carried out the instructions in order by converting them into macrocode.
4. Storing: The CPU may be required to store the result of an instruction in memory.
1. Fetching: Before the CPU can execute an instruction, the control unit must retrieve or fetch a command or data from the computer's memory.
2. Decoding: Before a command can be executed, the control unit must decode the command into instruction set.
Execution cycle: In execution cycle CPU also takes two steps--
3. Executing: When the command is executed, the CPU carried out the instructions in order by converting them into macrocode.
4. Storing: The CPU may be required to store the result of an instruction in memory.
| pipelining/non-pipelining |
In computers, a pipeline is the continuous and somewhat overlapped movement of instruction to the processor or in the arithmetic steps taken by the processor to perform an instruction. Pipelining is the use of a pipeline. Without a pipeline, a computer processor gets the first instruction from memory, performs the operation it calls for, and then goes to get the next instruction from memory, and so forth. While fetching (getting) the instruction, the arithmetic part of the processor is idle. It must wait until it gets the next instruction. With pipelining, the computer architecture allows the next instructions to be fetched while the processor is performing arithmetic operations, holding them in a buffer close to the processor until each instruction operation can be performed. The staging of instruction fetching is continuous. The result is an increase in the number of instructions that can be performed during a given time period.
Pipelining is sometimes compared to a manufacturing assembly line in which different parts of a product are being assembled at the same time although ultimately there may be some parts that have to be assembled before others are. Even if there is some sequential dependency, the overall process can take advantage of those operations that can proceed concurrently.
Computer processor pipelining is sometimes divided into an instruction pipeline and an arithmetic pipeline. The instruction pipeline represents the stages in which an instruction is moved through the processor, including its being fetched, perhaps buffered, and then executed. The arithmetic pipeline represents the parts of an arithmetic operation that can be broken down and overlapped as they are performed.
Pipelines and pipelining also apply to computer memory controllers and moving data through various memory staging places.
to understand more :
machine cycle
pipelining
