Editing Branch predictor (section)

===Overriding branch prediction===
The [[trade-off]] between fast branch prediction and good branch prediction is sometimes dealt with by having two branch predictors. The first branch predictor is fast and simple. The second branch predictor, which is slower, more complicated, and with bigger tables, will override a possibly wrong prediction made by the first predictor.

The Alpha 21264 and Alpha EV8 microprocessors used a fast single-cycle next-line predictor to handle the branch target recurrence and provide a simple and fast branch prediction. Because the next-line predictor is so inaccurate, and the branch resolution recurrence takes so long, both cores have two-cycle secondary branch predictors that can override the prediction of the next-line predictor at the cost of a single lost fetch cycle.

The [[Intel Core i7]] has two [[branch target predictor|branch target buffers]] and possibly two or more branch predictors.<ref>{{cite patent |inventor1-last=Yeh |inventor1-first=Tse-Yu |inventor2-last=Sharangpani |inventor2-first=H. P. |publication-date=2000-03-16 |title=A method and apparatus for branch prediction using a second level branch prediction table |country-code=WO |postscript=<!--None--> |patent-number=2000/014628}}</ref>