Advanced Computer Architecture, Imperial College 2001
23
Prediction pay-off
•
Prediction pay-off
matrix shows costs of
false negatives and false
positives
PNAN
True negative
PNAT
false negative
Predicted
not-taken
PTAN
false positive
PTAT
true positive
Predicted
taken
Actually
not-taken
Actually
taken
Actual branch
delay is
P
PTAT
*C
PTAT
+
P
PNAT
*C
PNAT
+
P
PTAN
*C
PTAN
+
P
PNAN
*C
PNAN
Asymmetry
: is it
better to have a
false negative, or a
false positive?