{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

InClassActivity17-sol

# InClassActivity17-sol - SOLUTION In-Class Activity#17 6:51...

This preview shows pages 1–2. Sign up to view the full content.

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)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 2

InClassActivity17-sol - SOLUTION In-Class Activity#17 6:51...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online