01 - ILP

Question 1

refers to an activity, item of information, material, or product, that is between the starting point and the completion point

Answer 1

pipeline

Question 2

a pipeline is __ or __ in nature

Answer 2

sequential, linear

Question 3

a pipeline is typical in __ and __

Answer 3

manufacturing, assembly lines

Question 4

refers to an implementation technique where multiple instructions are overlapped in execution

Answer 4

pipelining

Question 5

cons of not implementing pipelining (3)

Answer 5

1. resources are wasted
2. machines are not used at some point
3. time is not optimized

Question 6

refers to the three stages that compose a pipeline

Answer 6

fetch, decode, execute

Question 7

true or false:

pipeline stages may vary and can have 5 stages, with 3 stages being the least

Answer 7

true, it varies depending on the design

Question 8

refers to the degree to which, on average, the instructions of a program can be executed in parallel

Answer 8

instruction-level parallelism

Question 9

refers to the stage that must be present in order to ensure correctness whenever stages do not properly align or data hazards are present

Answer 9

stall

Question 10

on ILP:

we are concerned with maximizing the __ while keeping the correctness of the result

Answer 10

number of instructions that are executed in parallel

Question 11

which of the following statement/s is/are true?

on the ideal pipeline:

a. all objects go through the same stages
b. sharing of resources is allowed between stages as long as they are not sequentially executed

Answer 11

a only, no sharing of resources between any two stages

Question 12

__ through all pipeline stages is equal

Answer 12

propagation delay

Question 13

scheduling of a transaction entering the pipeline is [affected/not affected] by the transactions in other stages

Answer 13

not affected

Question 14

true or false:

the time consumed by a five stage pipeline is greater than the maximum between the time per stage (fetch, decode, execute, memory, write)

Answer 14

true

Question 15

on the time consumed by a five-stage pipeline:

the max time consumed is typically the time spent on __, for most of the processors

Answer 15

memory

Question 16

what does CPI stand for?

Answer 16

cycles per instruction

Question 17

CPI is [increased/decreased] when instructions are pipelined

Answer 17

increased

Question 18

formula for time per program (time/program)

Answer 18

time/program = (instructions/program) * (cycles/instruction) * (time/cycle)

Question 19

CPI depends on __ and __

Answer 19

ISA, microarchitecture

Question 20

time/cycle depends on __ and __

Answer 20

microarchitecture, technology used

Question 21

refers to the execution of an action

Answer 21

performance

Question 22

refers to work done based on a given set of resources

Answer 22

performance

Question 23

performance, in pipelining, are typically measured through: (3)

Answer 23

1. CPI
2. average instruction execution time
3. speedup

Question 24

formula for CPI

Answer 24

sum(numOfInstForInstrType * clkCycleForInstType) / totalNumberOfInsts

Question 25

Suppose an N-segment pipeline processes M instructions without stalls or penalties. We know that it takes N-1 cycles to load (setup) the pipeline, and M cycles to complete the instructions . Thus, the number of cycles is given by:

Answer 25

Ncyc = N + M - 1

Question 26

formula for CPI given Ncyc = N + M - 1

Answer 26

CPI = Ncyc / M CPI = 1 + ((N - 1) / M)

Question 27

formula for number of cycles with stalls

Answer 27

Ncyc = N + M + K - 1

Question 28

formula for CPI with stalls

Answer 28

CPI = 1 + (N + K - 1)/M

Question 29

formula for the average instruction execution time of an unpipelined processor

Answer 29

Clock cycle * Average CPI

Question 30

Formula for speedup from pipelining

Answer 30

AveInstrTimeUnpipelined / AveInstrTimePipelined