Pipelining

Pipelining

Computer Organization

What is pipelining?

• Pipelining is the process of accumulating instruction from the processor through a pipeline. It allows storing and executing instructions in an orderly process. It is also known as pipeline processing.

• Before moving forward with pipelining, check these topics out to understand the concept better :

  1. Memory Organization 2. Memory Mapping and Virtual Memory 3. Parallel Processing

Pipelining

Pipelining is a technique where multiple instructions are overlapped during execution. Pipeline is divided into stages and these stages are connected with one another to form a pipe like structure. Instructions enter from one end and exit from another end.

Pipelining

• Pipelining increases the overall instruction throughput.

• In pipeline system, each segment consists of an input register followed by a combinational circuit. The register is used to hold data and combinational circuit performs operations on it. The output of combinational circuit is applied to the input register of the next segment.

Pipeline

Pipeline system is like the modern day assembly line setup in factories. For example in a car manufacturing industry, huge assembly lines are setup and at each point, there are robotic arms to perform a certain task, and then the car moves on ahead to the next arm.

Types of Pipeline

• Arithmetic Pipeline

• Instruction Pipeline

Arithmetic Pipeline

Arithmetic pipelines are usually found in most of the computers. They are used for floating point operations, multiplication of fixed point numbers etc. For example: The input to the Floating Point Adder pipeline is:

Arithmetic Pipeline

• The floating point addition and subtraction is done in 4 parts:

  1. Compare the exponents. 2. Align the mantissas. 3. Add or subtract mantissas 4. Produce the result.

• Registers are used for storing the intermediate results between the above operations.

Instruction Pipeline

• In this a stream of instructions can be executed by overlapping fetch, decode and execute phases of an instruction cycle. This type of technique is used to increase the throughput of the computer system.

• An instruction pipeline reads instruction from the memory while previous instructions are being executed in other segments of the pipeline. Thus we can execute multiple instructions simultaneously. The pipeline will be more efficient if the instruction cycle is divided into segments of equal duration.

Pipeline Conflicts

There are some factors that cause the pipeline to deviate its normal performance. Some of these factors are given below:

1. Timing Variations

All stages cannot take same amount of time. This problem generally occurs in instruction processing where different instructions have different operand requirements and thus different processing time.

2. Data Hazards

All stages cannot take same amount of time. This When several instructions are in partial execution, and if they reference same data then the problem arises. We must ensure that next instruction does not attempt to access data before the current instruction, because this will lead to incorrect results.

3. Branching

All stages cannot take same amount of time. This In order to fetch and execute the next instruction, we must know what that instruction is. If the present instruction is a conditional branch, and its result will lead us to the next instruction, then the next instruction may not be known until the current one is processed.

4. Interrupts

Interrupts set unwanted instruction into the instruction stream. Interrupts effect the execution of instruction.

5. Data Dependency

Interrupts set unwanted instruction into the It arises when an instruction depends upon the result of a previous instruction but this result is not yet available.

Advantages of Pipelining

• The cycle time of the processor is reduced.

• It increases the throughput of the system

• It makes the system reliable.

Disadvantages of Pipelining

• The design of pipelined processor is complex and costly to manufacture.

• The instruction latency is more.

Time to test your knowledge

Are you ready for the quiz? If yes, click next!

Multiple Choice

1. How many types of Pipelining exist?

• 2

• 3

• 4

• 5

Multiple Choice

2. Arithmetic Pipeline is used for?

• floating point operations

• interger operations

• character operations

• None of the above

Multiple Choice

3. Which of the following is not a Pipeline Conflicts?

• Timing Variations

• Branching

• Load Balancing

• Data Dependency

Multiple Choice

4. Which of the following is disadvantage of Pipelining?

• cycle time of the processor is reduced.

• The design of pipelined processor is complex and costly to manufacture.

• The instruction latency is more.

• Both B and C

Multiple Choice

5. Which of the following is an advantage of pipelining?

• Instruction throughput increases.

• Faster ALU can be designed when pipelining is used.

• Pipelining increases the overall performance of the CPU.

• All of the above

Multiple Choice

6. The processor contends for the usage of the hardware and might enter into a

• hazard state

• Stalk State

• . Deadlock State

• None of the above

Multiple Choice

7. The Tomasulo algorithm is a hardware algorithm developed ___________.

• 1966

• 1967

• 1968

• 1969

Multiple Choice

8. In Arithmetic Pipeline, the floating point addition and subtraction is done in ____________ parts.

• 2

• 3

• 4

• 5

Multiple Choice

9. ______ have been developed specifically for pipelined systems.

• Utility software

• Speed up utilities

• Optimizing compilers

• None of the above

Multiple Choice

10. The pipelining process is also called as ______

• Assembly line operation

• Von Neumann cycle

• Superscalar operation

• None of the above