8.2 Pipelining

Question 1

Describe the laundy pipelining example

Answer 1

Question 2

What are the 4 stages of the fetch-execute cycle

Answer 2

Question 3

What does FDEW pipelining look like (instruction pipelining)

Answer 3

Question 4

What is the problem with long-latency instructions (pipelining)

Answer 4

Slowest operation determines throughput

Often specialised approximation hardware for square roots

Question 5

What is CPI (cycles per instruction)

Answer 5

1 instruction ie fetch-decode-execute-writeback

Question 6

What is a hazard (pipelining)

Answer 6

Something which causes the instruction pipeline to stall

Question 7

What are the main 3 types of pipelining hazards

Answer 7

Question 8

What is the RAW (read after write) data dependency

Answer 8

True data dependency (v1 used in s2)

Question 9

What is the WAR (write after read) data dependency

Answer 9

Need to make sure they are executed sequentially (ie problem for concurrency)

Question 10

What is the WAW (write-after-write) data dependency

Answer 10

Need to make sure they are executed sequentially (ie problem for concurrency). Last overwrites first.

Question 11

What are some methods to deal with data dependencies

Answer 11

Question 12

How do conditional branch instructions affect pipelining

Answer 12

“Undo” wrongly executed instructions.

Question 13

How is spectre / meltdown related to pipelining

Answer 13