Question

What type of conflicts arise when an instruction depends on the result of a previous instruction, but this result is not yet available?

• A. Data dependency
• B. Instruction dependency
• C. Operator dependency
• D. Branch dependency

Hint:

Whenever an instruction needs a result generated by an earlier instruction, a Data Dependency occurs.

Answer 1

The Correct Option is A

Concept: In pipelined processors, multiple instructions execute simultaneously in different stages. Sometimes an instruction requires data that is being produced by a previous instruction. When this happens, a dependency occurs. Such conflicts are called data dependencies or data hazards.

Step 1: Understand pipelining.
Consider the instructions: \[ I_1:\quad R_1=R_2+R_3 \] \[ I_2:\quad R_4=R_1+R_5 \] Instruction \(I_2\) requires the value of \(R_1\).

Step 2: Identify the conflict.
If \(I_1\) has not yet completed its execution, \[ R_1 \] is not available. Therefore \(I_2\) must wait. This creates a dependency on data.

Step 3: Name the dependency.
Such a situation is known as \[ \boxed{\text{Data Dependency}} \] or Data Hazard. Hence option (A) is correct.