BTB_BTCnotes

BTB_BTCnotes - BRANCH TARGET BUFFER/CACHE(BTB/BTC TO...

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EE557 Michel Dubois USC 2007 Chapter3.33 2/21/07 BRANCH TARGET BUFFER/CACHE(BTB/BTC) TO ELIMINATE THE BRANCH PENALTY NEED TO KNOW THE TARGET ADDRESS BY THE END OF IF INSTRUCTION HAS NOT BEEN DECODED THE BTB (BTC) IDEA CACHE FOR TAKEN BRANCHES (NO ALIASING) ACCESSED IN IF IN PARALLEL WITH INSTRUCTION IF HITS THEN BRANCH PREDICTED TAKEN index BTB PC: tag tag target address =? no: PC<-PC+4 PC<-Target address
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EE557 Michel Dubois USC 2007 Chapter3.34 2/21/07 BRANCH TARGET BUFFER CACHE FOR ALL BRANCHES 1-BIT PREDICTOR ADDED CAN BE COMBINED WITH ANY BRANCH PREDICTION SCHEME (BHT AND BTB ARE TOTALLY DECOUPLED) PREDICTING INDIRECT JUMPS procedure return is major source. Use a stack as return predictor index BTB PC: tag tag target address =? no: PC<-PC+4 PC<-Target T/NT address T? yes no: PC<-PC+4 yes
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EE557 Michel Dubois USC 2007 Chapter3.35 2/21/07 INCORPORATING A BTB IN THE 5-STAGE PIPELINE BTB CONTAINS TAKEN BRANCHES ONLY ASSUME HERE THAT BRANCHES ARE EXECUTED IN ID STAGE. IN IF STAGE:
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This note was uploaded on 03/19/2008 for the course EE 577B taught by Professor Bhatti during the Spring '08 term at USC.

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BTB_BTCnotes - BRANCH TARGET BUFFER/CACHE(BTB/BTC TO...

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