Computer Architecture Flashcards
What is abstraction?
Exclude aspects not required to focus on
the general characteristics needed
What is performance?
1/Execution Time
How to increase CPU performance?
Reducing number of clock cycles
Increasing clock rate
Hardware designer must often trade off clock
rate against cycle count
reduce leakage current occurring also when
transistor in off state
What is Amhalhs law?
States that the performance enhancement possible with a given improvement is limited by the amount that the improved feature is used.
What is In-lining or inline expansion?
A procedure which replaces a call to a function by the body of the function.
What is loop unrolling?
involves taking a loop, replicating the body multiple times, and executing the transformed loop fewer times. This will reduce the loop overhead.
Why a single-Cycle implementation is not used today?
The clock cycle must be the same for every instruction
The overall performance is poor since the clock cycle is too long
What is pipelining?
Implementation technique in which multiple instructions are overlapped in execution.
What are pipelining hazards?
Situations in pipelining when the next instruction cannot execute in the following clock cycle
Structural hazard- when hardware cannot support the combination of instructions that we want to execute in the same clock cycle. Occurs if we have a single memory instead of two memories.
Data hazard- when a planned instruction cannot execute in the proper clock cycle because data that is needed to execute the instruction is not yet available. Occurs from the dependence of one instruction on an earlier one that is still in the pipeline
Control hazard- when the proper instruction cannot execute in the proper pipeline clock cycle because the instruction that was fetched is not the one that is needed; that is, the flow of instruction addresses is not what the pipeline expected
What is branch prediction?
A method of resolving a branch hazard that assumes a given outcome for the branch and proceeds from that assumption rather than waiting to ascertain the actual outcome
What is the principle of locality?
says that most programs don’t access all code or data uniformly
What is AMAT?
(Hit Time) + (1 -h) x (Miss Penalty)
a common metric to analyse memory system performance
