Despite having the same A9X & M9 chips, only the 9.7" iPad Pro has always-on 'Hey Siri'
In a continuing curious omission, every device that runs Apple's M9 motion coprocessor features support for always-listening "Hey Siri" -- except for the 12.9-inch iPad Pro.

Apple on Monday took the wraps off of a new 9.7-inch iPad Pro and the iPhone SE, both of which feature A9-series processors and the M9 coprocessor, and both of which support "Hey Siri" when running on battery power alone.
"Hey Siri" was first introduced last year with the iPhone 6s and iPhone 6s Plus. It's made possible by the special low-power processing of the M9, which allows "Hey Siri" voice controls can be invoked without touching the device or plugging it in.

Curiously, however, Apple's larger 12.9-inch iPad Pro does not support always-on "Hey Siri" voice controls, even though it too has the M9 chip. The jumbo-sized tablet only responds to "Hey Siri" commands when it is plugged into a power source.
It's unknown why Apple hasn't added always-on "Hey Siri" support for the 12.9-inch iPad Pro. The company says that the M9 is the core of the feature, so technically it should be possible. However, as of iOS 9.3, Apple notes in the Settings app that the feature requires that the iPad Pro be connected to power.
Beyond the iPhone 6s series, iPhone SE and 9.7-inch iPad Pro, "Hey Siri" can also be used with the Apple Watch, but users must first raise their wrist to activate the screen before speaking.

Apple on Monday took the wraps off of a new 9.7-inch iPad Pro and the iPhone SE, both of which feature A9-series processors and the M9 coprocessor, and both of which support "Hey Siri" when running on battery power alone.
"Hey Siri" was first introduced last year with the iPhone 6s and iPhone 6s Plus. It's made possible by the special low-power processing of the M9, which allows "Hey Siri" voice controls can be invoked without touching the device or plugging it in.

Curiously, however, Apple's larger 12.9-inch iPad Pro does not support always-on "Hey Siri" voice controls, even though it too has the M9 chip. The jumbo-sized tablet only responds to "Hey Siri" commands when it is plugged into a power source.
It's unknown why Apple hasn't added always-on "Hey Siri" support for the 12.9-inch iPad Pro. The company says that the M9 is the core of the feature, so technically it should be possible. However, as of iOS 9.3, Apple notes in the Settings app that the feature requires that the iPad Pro be connected to power.
Beyond the iPhone 6s series, iPhone SE and 9.7-inch iPad Pro, "Hey Siri" can also be used with the Apple Watch, but users must first raise their wrist to activate the screen before speaking.
Comments
Of course people are going to pissed off.
And you know this for sure because you know all the engineering involved with making it work? There may be something else required in order to make it work properly and/or efficiently. When Apple designed the original "Pro" maybe it simply came down to them not thinking it was really necessary in an iPad? And when they designed this NEWER model, they decided to add the feature.
The M9 coprocessor is an extremely low power unit that monitors input from various sensors - it would stand to reason those sensors would need to be directly linked to the M9. If the mic in the 12.9" Pro is not tied to the M9, then "Hey Siri" obviously will not work. Now, I'm only guessing all of this, because I don't really know either, but it makes sense.
Umm that's a stupid assumption to make considering the larger iPad is still on the shelves and simply flipping a software switch to add additional and desirable features could in fact increase sales now.
Guess Apple will have to make a brand new 3-d touch commercial with Aubrey: "I'm peeking my flight. I'm not peeking my flight. I'm peeking my... wait, my brand new iPhone doesn't do that..."
And I gave a plausible explanation why it's not on the NEWER 12.9" iPad Pro - When Apple designed that iPad, they simply decided "Hey Siri" wasn't a beneficial feature to have on an iPad.
But here's a couple more...
1. The iPad Pro was designed before the feature was considered or engineered.
2. "Hey Siri" was a completely new feature and they wanted a "limited" release.
3. The A9X SoC provided a design challenge that kept them from making the feature available in time for the Pro's release.
You are a fucking delusional mess. Always-on Hey Siri debuted in the fucking iPhone 6s, before the iPad Pro was released. The iPad Pro contains everything necessary for always-on Hey Siri. Then its counterpart version 4 months later sports the same hardware, and includes the feature.
That's all bullshit. The new 9.7" iPad Pro has the exact, EXACT, same fucking hardware. There is no excuse.
I'm pretty sure it does not have the exact same hardware... the motherboard is different, the video controller is different, the Lightning interface is different. And guess what!? The microphones might even be different!!!
The point of Apple's Motion processors is to monitor and process input from various sensors. In order for this to work efficiently the Motion processor would need a direct path to those sensors, so the main CPU can be completely bypassed. If for some reason Apple did not engineer the original iPad Pro so that the microphone had a direct path to the M9 and instead that data could only be accessed through the main CPU, then always on "Hey Siri" would not be possible. Having the main CPU constantly monitor and process audio input would eat through your battery charge - which is why every other device requires itself to be plugged in before enabling "Hey Siri".
LOL And you're calling other people delusional? You're the one who seems to be emotional beyond rational.
You do know the M9 motion processors are built-in to both the A9 and A9X, right?
That there is no special fab for some sort of fictional "Hey Siri" high-speed-bus-to-the-microphones on every A9X except the one for the large iPad Pro?
You made up all of the above (bolded), as if you had the first clue what you were talking about, then you have the gall to call other people "beyond rational"? Dude, you are a real piece of work.