ILP

Question 1

What does ILP stand for?

Answer 1

instruction level parallelism

Question 2

How do data dependencies affect the execution time of a program?

Answer 2

RAW (true) dependencies will be a limiting factor for the CPI, even if the CPU can perform everything else perfectly. More dependencies chains == higher CPI

Question 3

What is a false dependency?

Answer 3

WAR and WAW - these are false because they only exist because we’re using the same registers.

Question 4

What are architectural registers?

Answer 4

registers that the programmer compilers use (R1, R2, etc)

Question 5

What are physical registers?

Answer 5

all the places a value could be stored (not necessarily registers)

Question 6

What is register renaming?

Answer 6

Renaming architectural registers to a physical location where the data is stored. We use a Register Allocation Table (RAT) - maps architectural registers to physical registers

Question 7

What is ILP?

Answer 7

A property of the program, independent of the processor. It is the IPC if the processor had infinite resources. IPC >= ILP

Question 8

How do you compute the ILP?

Answer 8

Rename the registers (on paper or your head) and execute / compute the instructions / cycles