Whereas Intel's (INTC +1.3%) 22nm Haswell CPU architecture aims to deliver at least a 1% increase in performance for every 1% increase in power draw, its 14nm Broadwell architecture shoots for a 2% performance gain for each 1% power increase.
Together with the gains that come from smaller transistor sizes, Broadwell's power draw is improved with the help of 15% and 10% respective drops in capacitance and minimum operating voltage, and a sizable reduction in leakage.
In addition, Intel has improved the power draw of its platform controller hub (integrated within CPU packages) and voltage regulator ICs, and cut the amount of extra power required by its Turbo Boost mode.
On the performance front, Intel is aiming for a 5%+ increase in processed instructions per CPU clock cycle relative to Haswell, and will bundle an integrated GPU that supports the latest graphics APIs, thus addressing (as noted by AnandTech) a past shortcoming.
Systems based on Intel's tablet/ultrabook-focused Core M Broadwell CPUs (previous) are expected this holiday season. Intel wants to offer Core M CPUs with only 3W-5W of max power draw - all Core M parts will be under 10W - and which can be used in fanless ~10" tablets that are only 8mm-10mm thick. The Surface Pro 3 (uses Core i3/i5/ii7 CPUs) is only 9.1mm thick, but also contains a fan.
Stabilizing PC sales have lowered the pressure Intel faces to produce a mobile breakthrough. However, Broadwell/Core M is still pivotal to Intel's attempts to grab share from ARM-based mobile CPUs by enabling converged devices that fuse PC-like performance with low power draw and mobile-friendly form factors.