A few months ago, we detailed Intel's low-power plans with Haswell and how the company was planning to push mainstream x86 processors into much lower TDPs than it had previously discussed. Santa Clara still intends to deliver Haswell
parts at 10W or below, but it's accelerated the delivery of sub-10W parts even further. Today, it officially announced a series of chips with a 7W "Scenario Design Power."
SDP is a new-ish metric Intel is introducing with these new processors. SDP is defined as an additional thermal reference point based on mainstream workloads on tablet devices.
This is the sort of change-up that tends to touch off allegations of lying and misrepresentation. I'm going to try to head that off at the pass by noting that TDP is perhaps the worst metric for comparing products between the various ARM
manufacturers. Clock speed is a flawed metric, insomuch as frequency doesn't equate to performance, but it can at least get you in the ball park. When it comes to TDP, every manufacturer uses their own workloads and definitions.
A chip's TDP, according to Intel, is the amount of power its cooling solution
must be capable of dissipating to ensure the chip doesn't overheat. AMD used to define it as the maximum amount of power a chip was capable of dissipating. Every company uses different metrics to decide on a final TDP rating, even if they define TDP in the same way. Furthermore, different companies may include the power consumption of different system components in their final TDP ratings.
comparisons can't be trusted, Intel's decision to include SDP for tablets is a nod to the fact that these devices are used in very different ways. Intel hasn't given much detail on the difference between SDP and TDP, but we can make some educated guesses. Smartphones and tablets spend the majority of the time asleep. When Intel launched Medfield a year ago, we discussed how 0W has become the new 1GHz; smartphones and tablets are designed to race back to idle mode as quickly as possible.
In the chart below, nominal TDP is the standard TDP metric we're familiar with. The 10W cTDP Down number means that Intel guarantees the chip will draw 10W or less if the CPU temperature remains below 105C. In typical tablet scenarios, SDP will remain at 7W, provided the chip temperature is 80'C or less.
The bottom line, for consumers, is that these new chips could drive better, faster tablet experiences without compromising battery life. If that happens, we suspect the question of SDP by TDP will largely fall to the way side. As for where we'll see these chips, little birds we've talked to have said Microsoft's upcoming Surface Pro may <em>not</em> use these parts. If true, that's sure to raise some eyebrows. So far, Lenovo's Yoga 11S (on display at CES) is the one system we know of that's definitely based on the new CPUs.