InClassActivity17-sol

InClassActivity17-sol - SOLUTION In-Class Activity #17...

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SOLUTION In-Class Activity #17 11/29/07 6:51 PM Activity 17.1 (First Hour) I/O service Consider a processor with a 500KHz clock, and a hard disk that transfers data in 8-word chunks with a transfer rate of 10 MB/sec. a) (10 points) Assume the processor uses polling and that each polling operation (transferring to the polling routine, accessing the device, restarting the user program) takes 500 clock cycles. Assume you poll often enough so that no data is ever lost. What is the fraction of the CPU time consumed by polling? We must poll at the rate = 10 MB / sec = 327,680 transf / sec 32 byte / transfer Cycles per sec for polling = 327,680 x 500 = 163.84 x 10^6 Fraction of the CPU = 163.84 x 10^6 = 32.76% 500 x 10^6 Grading: 3 pts for each part, 2 minimum. b) (10 points) Assume we use interrupt-driven I/O and the overhead for each transfer is 400 clock cycles. What is the fraction of the CPU time consumed if the disk is transferring data 10% of the time? Cycles per sec for disk = 327,680 x 400 = 131 x 10^6 Fraction of the CPU consumed with constant usage = 131 × 10^6 = 26.2% 500 × 10^6 For 10% average use = 26.2% x 10% = 2.62% Grading: 3 pts for each part, 2 minimum. c)
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This homework help was uploaded on 04/08/2008 for the course ECE 562 taught by Professor Zhou during the Fall '07 term at New Hampshire.

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InClassActivity17-sol - SOLUTION In-Class Activity #17...

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