1. The OS controls an I/O device by a) sending a message to the device’s port, b
ID: 3718722 • Letter: 1
Question
1. The OS controls an I/O device by a) sending a message to the device’s port, b) using CPU instructions specific to that device, or c) writing to registers in the device’s controller.
2. Which of the following is not a way for for the OS to interact with an I/O device: a) DMA, b) programmed I/O, c) handling I/O interrupts, or d) a data link protocol
3. A disk drive has a speed of 12000 RPM, an average seek time of 5 ms, and a transfer rate of 140 MB/sec. How much time does it take to perform 50 random reads of 10 KB? (In other words, the 50 reads are from random spots on the drive, but each individual read is performed sequentially.) Give your answer in units of seconds.
4. Given the same information as in c) above, what is the I/O rate for the 50 reads? Give your answer in MB/sec.
5. When a Linux directory is first created, how many entries does it contain? a) 0 b) 1 c) 2 d) 16
6. On hosting, what type of file system is /home/CLASSES? a) ext3, b) ext4, c) tempfs (hint: when a volume is mounted, the file system type is given. See the ‘mount’ man page.)
Explanation / Answer
Answers)
1. The OS controls an I/O device by
c) writing to registers in the device’s controller.
A way of communicating with the I/O device is by communicating with the registers associated with each port and thus writing to registers in the device’s controller is one way in which the OS can control the I/O device.
2. Which of the following is not a way for for the OS to interact with an I/O device: a) DMA, b) programed I/O, c) handling I/O interrupts, or d) a data link protocol
Answer) d) a data link protocol is not associated with the way for for the OS to interact with an I/O device. It is a networking protocol.
a) DMA, b) programed I/O and c) handling I/O interrupts are ways of the OS to interact with an I/O device.
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