I/O Systems

Question 1

Port

Answer 1

Connection point for devices

Question 2

Bus

Answer 2

Daisy chain or shared direct access

• PCI
• Expansion bus

Question 3

Controller (host adapter)

Answer 3

A collection of electronics that can operate a port, a bus, or a device.

Question 4

True or False? Most CPUs allow some interrupts to be ignored so that a
critical instruction cannot be interrupted.

Answer 4

True

Question 5

True or False? A given device may require different drivers for different
operating systems.

Answer 5

True

Question 6

What is an alternative to a nonblocking system call?

Answer 6

Asynchronous System Call

Question 7

Polling

Answer 7

Can happen in 3 instruction cycles:

1. read status
2. logical-and to extract status bit
3. branch if not zero

Question 8

Interrupt Request Line

Answer 8

Hardware lines over which devices can send interrupt signals to the microprocessor

Question 9

What are the two conflicting trends of I/O devices?

Answer 9

1. Increased standardization of software and hardware interfaces.
2. An increasingly broad variety of I/O devices.

Question 10

List at least three different services provided by the kernel I/O subsystem.

Answer 10

1. Scheduling
2. Buffering
3. Caching

• 4. Spooling
• 5. Device Reservation
• 6. Error Handling

Question 11

True or False? The lifecycle of an I/O request does not require many
CPU cycles.

Answer 11

False

Question 12

What operating system is the STREAMS mechanism designed for?

Answer 12

UNIX System V

Question 13

True or False? I/O operations do not have a significant impact on
performance.

Answer 13

False