How?

It isn't directly comparable. I've got a PS4 and still want a Switch. The Switch is a portable console that also functions as a home console and entry level VR system. Was the 3DS directly in competition with PS4, no but indirectly yes for those who weren't sure if they wanted a console with portability or a permanent home console. Are there many consumers like that?

A huge number of wii owners also owned a ps3 or 360. The idea that every household only has one console is not realistic or representative of reality. 

I plan to buy a Switch with VR HMD and one extra dock so I can use the console both in my living room and one room upstairs. In the UK that may cost me £250 plus maybe £25 or £30 for an extra dock with psu. So £280 in total. That effectively gets me 2 home consoles, a portable and a VR system because it easy to just move the tablet between docks between rooms.

Well, but people that wanted to believe that Switch would outperform X1 there wasn't a reason for them to be bond for such things as reliable sources... Some would even defend the sources citing that they were claimed as thrustworthy.

But anyway, the specs are bellow what most thought would be.

No, even portable mode should outperform Wii U.

Mate this makes no sense as you seem to be under the impression that the whole portable market is going to just vanish or doesn't exist, 3DS sold well because it's the better platform for the portable market. PS4 and X1 have no bearing on that because they're not portable devices, a portable gamer is not going to opt for a PS4 or X1 because they can't get portable gaming from it plus a significant number probably already own those platforms so in a sense if the other user said portable games will help it do 3DS numbers he's right as that's what attracts them only now they have a massive jump in power, this is why your post is coming across as confusing.

Switch has no equivalent alternative for dedicated portable gaming which further helps his point.

When Nvidia and AMD build a GPU, they bunch up the GPU cores in units (that has everything those cores need, and call it 1 SM).

One such bunch of cuda cores is called a SM, it stands for Streaming Multiprocessor.

Inside a SM are stuff like: the cores, store/load units, special funktion units ,highspeed memory cache (L1 & shared, and L2), and a interface the connects them all.

this is a diagram from a Nvidia Fermi:  https://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Fermi.svg/368px-Fermi.svg.png

^ each GPU has many of these inside them.

Thats what the 2 or 3, part your in question is about.

Their talking about how many "Cores" inside the Tegra X1 chip, there will be.

The most reasonable assumption is its the standard amount, that the Tegra X1 in all other products comes with.

Why? well its already more powerfull than what they need, if their downclocking it so much.

Why build a bigger chip, if its already more than you need? you dont.

You save a ton of Research & Developement money, just useing the chips Nvidia already has.

And why would you deem such a scenario impossible? The Xbox One S is using old inefficient technology. (Not stating the Switch is using cutting edge either but.)

Again, Volta powered Tegra should drop next year, which should be Xbox One levels of performance, built at the same 16nm Finfet at TSMC and use a fraction of the energy.

nVidia has the efficiency edge even against AMD.
Even nVidia's 28nm maxwell chips can give AMD's 14nm Polaris chips a run for it's money in regards to performance/effeciency.

And there are a ton of reasons why.

That Nvidia coolaid :p

The Tegra X1 uses like 30watts of power to reach those 512 Gflops its able to do in the shield console.

Without powering a screen or anything extra.

Hell a Hard disk drive is 4-5watts alone, and PS4 & XB1 use those.

Even if Nvidia tried to do a 1teraflop Mobile chip, it would still be in the 50+watt range.

You make it sound like the Chips inside the PS4 & XB1 are bad, and their really not.

Not at the power levels of graphics they do.

This chart is useing old review scores, but AMD drivers for the 470/480 have done alot since it released.

And look at that the most effecient GPU chip at 1920x1080 resolutions is a RX 470!

I think you may have copied the wrong chart.

omg thats..... embarrassing >_>

I swore I hit the performance pr watts part... lol.

Im gonna end up looking like a arse.

Right Chart:

Yeah RX470/480 arnt at the top of the list.

Will say this though; the launch drivers for the RX470/80 wherent the best optimised, newer drivers have seen some pretty decent gains.

Its something nvidia is usually good about, optimiseing drivers for launch so their cards revew well day1.