Reply To: Meltdown and Spectre

The real win with a predictor is not in avoiding miss rewinds (at least on a Mill where a miss is five cycles) which the authors scheme helps with, it’s in moving instruction lines up the memory hierarchy.

In a top-end OoO it’s perhaps more true to say the real win is filling the reorder buffer. Your predictor doesn’t have to be that good to deal with fetching code in time, given caches are getting so large and looping is so common, but if you want to fill a 560ish instruction ROB, you need to be predicting 560 instructions ahead, and predictor quality and performance is intensely important for that. But yeah, that’s not so relevant for a Mill.