3 ms·
You could do it, but 'work' produces heat. From that point of view a branch predictor /saves/ you from spending the heat of the cases you /don't/ need to have
by mjevans 9y ago
You could do it, but 'work' produces heat.
From that point of view a branch predictor /saves/ you from spending the heat of the cases you /don't/ need to have processed.
The performance per watt of such a design would probably leave it on the back of a napkin as an educated guess of how costly that would be.
- Simon_says 9y agoPie-in-the-sky idea here, but only irreversible computations produce heat. Maybe in the distant future we can make chips that do many parallel computations of all branches reversibly, and only make the results irreversible once the correct branch is known?
- dfox 9y agoIn theory, irreversible computations have to produce heat, while reversible do not. In practice this is mostly irrelevant, because the heat involved is so minuscule that there will always be other significantly larger sources of inefficiency involved. Also it is somewhat questionable whether one could actually construct physical realization of useful logic primitive that is truly reversible.
- deepnotderp 9y agoYes, but functional units are only around ~6% of the power consumption of a modern superscalar processor. And with Moore's law squeaking out its last few iterations, that number will get even smaller. If you can remove a good part of that by using predication, then you actually win out on power and heat as well.