What are the two types of branch prediction techniques available?
Branch prediction technique can be of two types: Static Branch Prediction Technique. Dynamic Branch Prediction Technique.
What is a 2 level branch predictor?
Two-level predictor. The Two-Level Branch Predictor, also referred to as Correlation-Based Branch Predictor, uses a two-dimensional table of counters, also called “Pattern History Table”. The table entries are two-bit counters.
What are the two stage of the dynamic branch prediction?
1. Integrated branch prediction—The branch predictor becomes part of the instruction fetch unit and is constantly predicting branches, so as to drive the fetch pipeline. 2. Instruction prefetch—To deliver multiple instructions per clock, the instruction fetch unit will likely need to fetch ahead.
What is branch prediction explain various schemes?
2 Branch Prediction and its Techniques Basically branch prediction predicts two problems: 1) direction predicting, and 2) calculating the target address. Branch prediction schemes are of two types: static branch schemes and dynamic branch schemes. A static branch scheme (software techniques) is very simple and easy.
What is called static and dynamic branch prediction?
Static branch prediction makes fixed prediction of a branch to either taken or not taken; Dynamic branch prediction makes prediction based on previous history situation, by looking at history table.
What is bimodal branch predictor?
The most well known technique, referred to here as bimodal branch prediction, makes a prediction based on the direction the branch went the last few times it was executed. More recent work has shown that significantly more accurate predictions can be made by utilizing more branch history.
How does a general level 2 predictor work?
The two-level predictor uses one or more arrays of 2-bit saturating up-down counters, called Pattern History Tables, to keep track of the more-likely direction for branches.
What is branch prediction and speculative execution?
Branch prediction is done by the processor to try to determine where the execution will continue after a conditional jump, so that it can read the next instruction(s) from memory. Speculative execution goes one step further and determines what the result would be from executing the next instruction(s).
What is dynamic branch prediction logic?
To avoid this problem, Pentium uses a scheme called Dynamic Branch Prediction. In this scheme, a prediction is made for the branch instruction currently in the pipeline. The prediction will either be taken or not taken. If the prediction is true then the pipeline will not be flushed and no clock cycles will be lost.
Do unconditional jumps need branch prediction?
Unconditional branches are not a problem for the branch predictor, because the branch predictor doesn’t have to predict them.
How accurate is branch prediction?
This scheme was implemented in the MIPS R10000 processor and the results showed prediction accuracy of ~90%.
How many cycles does Branch Prediction take?
On modern processors it takes between one and twenty CPU cycles. There are at least four categories of control flow instructions: unconditional branch (jmp on x86), call/return, conditional branch (e.g. je on x86) taken and conditional branch not taken.