[chx]

So far ARM in servers has proven to be a disaster performance per watt-wise. Intel's Xeon D CPUs are not even the latest microarchitecture and yet they are wiping the floor with any other chip trying to get the performance per watt crown. Look up some Xeon D-1587 benchmarks (16 Broadwell cores at 1.7 GHz in a 65W envelope).

And since then Intel has picked up another 30% at least in performance/watt by going from Broadwell to Kaby Lake and soon Coffee Lake and so they can answer any challenger if they so want.

The reason there's no Skylake Xeon D is that Intel doesn't need it yet.