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Unformatted text preview: these branches as being taken is generally a good idea. Forward branches, on the other hand, are used for conditional computation. Experiments have shown that the backward-taken, forward-not-taken heuristic is correct around 65% of the time. Predicting all branches as being taken, on the other other hand, has a success rate of only around 60%. Far more sophisticated strategies have been devised, requiring greater amounts of hardware. For example, the Intel Pentium II and III processors use a branch prediction strategy that is claimed to be correct between 90% and 95% of the time . We can run experiments to test the branch predication capability of a processor and the cost of a misprediction. We use the absolute value routine shown in Figure 5.29 as our test case. This ﬁgure also shows the compiled form. For nonnegative arguments, the branch will be taken to skip over the negation instruction. 5.12. BRANCH PREDICTION AND MISPREDICTION PENALTIES 251 We time this function computing the absolute value of every element in an array, with the array...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.
- Spring '10
- The American