A system transfer data blocks of 2000 bytes with programmed I/O, each byte…

2026

A system transfer data blocks of 2000 bytes with programmed I/O, each byte transfer takes 6 CPU cycles, with direct memory access (DMA), the block transfer takes 3000 Cycles total, with CPU setup overhead of 200 cycles. The CPU clock is 1 GHZ.

How much CPU time is consumed by programmed I/O?

  1. 12 μs

  2. 20 μs

  3. 24 μs

  4. 30 μs

  1. A.

    1

  2. B.

    2

  3. C.

    3

  4. D.

    4

Attempted by 118 students.

Show answer & explanation

Correct answer: A

Step-by-Step Solution

To find the CPU time consumed by programmed I/O, we calculate the total cycles and convert them to time.

1. Calculate Total Cycles

Total Cycles = Block Size × Cycles per Byte

Total Cycles = 2000 bytes × 6 cycles/byte = 12,000 cycles

2. Convert Cycles to Time

Time = Total Cycles / Clock Frequency

Clock Frequency = 1 GHz = 1 × 10^9 Hz

Time = 12,000 cycles / (1 × 10^9 cycles/second) = 0.000012 seconds

Convert to microseconds: 0.000012 seconds × 10^6 μs/s = 12 μs

Conclusion

The CPU time consumed by programmed I/O is 12 μs.

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