Power Consumption Improvements
When talking about the Haswell processor generation, Intel doesn’t hide the fact that they primarily focused on the interests and needs of the mobile systems users. In other words, lowering the power consumption and heat dissipation were practically the major objectives all the way. And they have indeed done everything possible to achieve maximum power and heat reduction: maximum optimization of the semiconductor design and process technology, improvement of the core and uncore, addition of new software controlled power-saving states.
The optimized production process will obviously allow lowering the semiconductor die power consumption as a whole. However, in Haswell they have fine grained power control. The unutilized parts of the processor will be simply disabled in a very aggressive manner. Moreover, the cores, L3 cache memory and processor integrated graphics will work at different frequencies, which will be adjusted individually depending on the type of performed tasks.
Power-saving states have also been completely refreshed. By disabling “unutilized” units, Intel managed to lower the processor power consumption in idle mode and also improve the transition times from idle to active mode significantly. Namely, they have improved the existing C-states and added new deeper C-states and sped up the transition between them by up to 25%.
The particularly cool feature is the new S0xi state, in which the processor idle mode power consumption has become at least 20 times lower than what the previous generation processors had to offer. Moreover, there should be no negative side effects upon transition from this state into the active mode.
According to Intel, S0ix, will allow Haswell to find its way to tablets and smartphones. It is true, the S0xi state combines the advantages of the S0 and S3/S4 states lowering the power consumption to the minimal level of hundreds of milliwatts without requiring too much time to recover from this state. While in this state, the OS and applications think that the platform is active but the achieved power levels are the same as were previously associated with the sleep state. It offers completely different state of idle power and the responsiveness is always on. In other words, it is the best of both worlds. This is where we get tremendous improvement in battery life and transition times become shorter and we achieve lower power states much quicker. It is continuous, fine-grain (at the smallest levels) and transparent to well-written software. So far Intel found that most software works just fine with it the way it is.
Haswell also has improved Turbo Boost technology. Intel now can do better load balancing to the power side of the chip to extend their Turbo range. But it is about doing a much finer-grain control for each of the units on the die, where you do not waste power on performance.
Moreover, the platform itself has been optimized for maximum energy-efficiency. The link between the CPU and the chipset has been optimized for power. And that is far not all that has been done: Intel encourages its partners to address the energy-efficiency aspect carefully, too. Namely, they have been working closely with the vendors and did a new power allocation for idle states. It allows the manufacturers to meet power goals on the platform level. Intel also worked very hard on optimizing controllers, voltage regulators (efficiency improvements), and bringing new innovations to the platform in terms of power architecture. They have added a number of low-power IO standards, which gave OEMs and ODMs flexibility in terms of picking the devices with the best suited power characteristics.
So, a lot of really exciting innovations got in the Haswell platform in terms of power efficiency and power management. Intel is developing a 10W TDP processor for even greater battery life and reduced heat, which leads to thinner as well as lighter Ultrabooks. Due to reduced watt-usage the performance level won't be as strong as from the Ivy Bridge CPU at 17W.
The Windows 8 does have fully-fledged support of all power-saving innovations, so their actual adoption should go quickly and painlessly.