> Also, since modern CPUs internally have many functional units to which operations can be dispatched, I wonder if, in the case that the "confidence" of a branc

> Also, since modern CPUs internally have many functional units to which operations can be dispatched, I wonder if, in the case that the "confidence" of a branch prediction is not high, "splitting" the execution stream and executing both branches in parallel until the result is known... This is called disjoint eager execution: http://dl.acm.org/citation.cfm?id=225208 http://dl.acm.org/citation.cfm?id=225208 What killed the idea is that branch predictors are simply too good. You'd end up almost never speculating off the main spine the predictor gives you, and so all the other machinery needed doesn't provide nearly enough value for its cost.