Week 12

Question 1

3 main functions of IO Driver:

Answer 1

Initialize Device
Manipulates device’s CSRs to start operations when I/O is needed
Handles interupts from devices

Question 2

What are the 2 type of IO devices?

Answer 2

Character Oriented: Keyboard, Mouse (Transfer one byte at a time)
Block-oriented: Disk, network interface (Transfer block of data at a time)

Question 3

What are the 3 parts of a device driver?

Answer 3

Lower Half, Upper half, shared variables

Question 4

Lower Half:

Answer 4

Handler code that is invoked when the device interrupts, communicates directly with device

Question 5

Upper half:

Answer 5

Set of functions that are invoked by applications, allows application to request I/O operations

Question 6

shared variables

Answer 6

used by both halves to coordinate, contains input and output buffers

Question 7

_____ is needed because interrupts occur asynchronously and multiple applications can attempt I/O on a given device at the same time

Answer 7

mutual exclusion: This guarantees only one operation will be performed at any time

Question 8

what is pipelining?

Answer 8

pipelining is when you execute multiple instructions at once in order to speed up the overall program (think laundry example)

Question 9

What is instruction-level parallelism?

Answer 9

parallelism that exists in machine programs

Question 10

what are the 3 hazards of pipelining?

Answer 10

Structural hazard: isufficient hardware exists for parallelism
data hazard: instruction depends on earlier result; pipelining overlap of instructions exposes this dependence
control hazard: caused by branches and instructions that change the PC away from Default_next_instruction

Question 11

what is dependece?

Answer 11

A program property whereby a sequential relationship exists between instructions because of the requirement for program correctness, limits ILP

Question 12

data dependece exists when:

Answer 12

a result is used (later) as an operand; such dependence is inherent to the algorithm used

Question 13

true data dependence:

Answer 13

a result is used later as an operand, a value flows from one instruction to an instruction appearing later in the program listing

Question 14

name dependence:

Answer 14

occurs when two instructions use the same storage location, called a name, but no value flows from the first instruction to the subsequent one

Question 15

antidepence from J to K

Answer 15

occurs when J reads from the name and K writes to the name

Question 16

output dependence from J to K

Answer 16

occurs when J and K both write to the name

Question 17

How do you view dependences as read / write actions:

Answer 17

No dependence: Read after Read, this is good and ILP exists
True Data Dependence: Read after Write
Antidependence: Write after Read
Output dependence: Write after Wright

Question 18

True or false: One register can be involved with multiple kinds of dependences simultaneously:

Answer 18

TRUE