Solution

The correct answer is 0.2 μs.

Key Points

• CPU setup overhead for DMA = 200 cycles.
• CPU clock speed = 1 GHz.
• 1 GHz = 10⁹ cycles per second.

Step-by-Step Solution

• Step 1: Convert clock speed to time per cycle
• 1 GHz = 10⁹ cycles/sec
• Time per cycle = 1 / 10⁹ sec
• = 10⁻⁹ sec per cycle
• Step 2: Compute time for 200 cycles
• Time = Cycles × Time per cycle
• = 200 × 10⁻⁹ sec
• = 200 × 10⁻⁹ sec
• Step 3: Convert to microseconds
• 1 μs = 10⁻⁶ sec
• Time = 200 × 10⁻⁹ / 10⁻⁶ μs
• = 200 × 10⁻³ μs
• = 0.2 μs

Additional Information

• DMA reduces CPU involvement to only setup time.
• Remaining transfer occurs independently of CPU.