I'm leaning more on the PPC side, because I honestly can't find an official source other than the twitter account that says Power 7, and note the power 7 rumours/ confirmation came because every was stating it was the same architecture as IBM Watson when in fact they were talking about the SOI technology and not the same architecture, from what I am gathering from this.
All modern power architectures (power4 and up) are ppc architectures, as they run on the instruction core that was started on power pc.
The official IBM power 7 Documentation I attached to this board refers to the Power 7 as a power pc architecture.
Power7 runs on ppc 2.06 instruction architecture.
This is where people who recieve second hand information, or dont really know what they are talking about get confused.
IBM has, from an official source bound by the legal agreements of ibm's standards of computer communications, stated, on multiple occasions, the wii u cpu is a custom power 7, the same processor core found in ibm watson.
For those with pr advertising nonsense in there heads thinking ibm is LYING for the sake of 'advertising' if it was a ppc 4xx series, they would have said it was the same processor family found in the Blue gene sequoia, the current fastest super computer in the world.
They would have truthful super computer pr either way. So why lie about watson?
There is no reason to name watson, and specifically state power 7 chips if its not using power 7. Those theories are nothing more than nonsense, and certainly not something Chris nays is willing to get fired over for breaching the ibm communications standards, when he could simply state, as he has done NUMEROUS times on the exact same twitter feed 'Thats not something ibm watson does.'