Question

Consider the following statements about bus arbitration schemes :
A. Daisy chaining is simple but slow

B. Parallel priority arbitration provides faster response than serial methods

C. Distributed arbitration allows multiple masters to share bus control

D. Centralized arbitration increases fairness

Choose the correct answer from the options given below :

• A. A, C, D only
• B. A, B, C only
• C. B, C, D only
• D. A, B, D only

Hint:

Daisy Chaining = Simple/Serial/Slow. Parallel = Complex/Fast. Distributed = No Single Point of Failure.

Answer 1

The Correct Option is B

Concept:
• Bus arbitration is the process by which the next "bus master" is selected when multiple devices request access to the shared bus.
• It can be categorized as Centralized (one arbiter) or Distributed (shared logic).

Step 1: Analyze Daisy Chaining (A)
In Daisy Chaining (a serial centralized scheme), the grant signal passes through each device in sequence. It is hardware-simple but the delay is proportional to the number of devices. Thus, A is correct.

Step 2: Analyze Parallel Arbitration (B)
Parallel schemes use independent request and grant lines for each device. All requests are evaluated simultaneously by the arbiter, leading to a much faster response than the serial daisy chain. Thus, B is correct.

Step 3: Analyze Distributed Arbitration (C)
In distributed schemes, each device has its own arbitration logic and they "compete" or "negotiate" for the bus. There is no single master controller. Thus, C is correct.

Step 4: Evaluate Fairness (D)
Centralized arbitration does not inherently increase fairness. In fact, basic centralized schemes like static priority daisy chains are notoriously unfair to devices far down the line. Fairness depends on the specific logic (like Round Robin) used, not whether the hardware is centralized or distributed. Thus, D is generally considered incorrect in a technical comparison.