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Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

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confidence level will drop below a confidence limit. <strong>The</strong> net effect of these parameters is<br />

that a prediction will be invalidated after three consecutive mispredictions. <strong>The</strong> valid and<br />

pending fields are used to determine which predictor entries can be used <strong>for</strong> predictor<br />

matches and which have outstanding predictions respectively. Multiple predictions can<br />

be outstanding. If conflicting prediction exist at an evaluation point, the higher<br />

confidence prediction is used. For equal confidence predictions, the lower index<br />

prediction is used. Additional details <strong>for</strong> each predictor field are provided in Table 7.2.<br />

An example of the PPPP tracking and predicting core utilization level is given in Figure<br />

7.6.<br />

Utilization<br />

Utilization<br />

80%<br />

20%<br />

80%<br />

20%<br />

1ms<br />

4ms<br />

Time (ms)<br />

2ms 2ms<br />

Time (ms)<br />

Figure 7.6: Example of Program Phase Mapping to Predictor<br />

133<br />

Pattern<br />

1ms,<br />

20%<br />

2ms,<br />

20%<br />

4ms,<br />

80%<br />

Pattern<br />

2ms,<br />

80%<br />

Pred.<br />

Phase<br />

4ms,<br />

80%<br />

Pred.<br />

Phase<br />

2ms,<br />

80%<br />

Time<br />

Stamp<br />

1ms<br />

Time<br />

Stamp<br />

2ms

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