I have 20 of those Xeon cores and 128Gb of RAM in a 2U.
Comparing the ratio of bogomips you'd have to get 598 of those ARM machines in a 2U to get the same bogomips.
Like I said this isn't even slightly scientific but is at least interesting trivia.
http://www8.hp.com/us/en/products/proliant-servers/product-d...
AMD will enter the market soon, too, but I think Applied Micro will hold its first mover advantage with its 3rd gen chips coming next year.
However if you want one fast core, you're screwed :)
I can probably push 40 of those onto it without it bending too terribly. If I knock the RAM down to 2Gb an instance I could probably quite happily get 64-100 on it in theory. I think memory bandwidth might kill it before CPU does.
We have two almost full (18 each) 42U racks of those machines (bar switches) so across the 720 E5 cores with 4.6TiB of RAM there is about 4.3 million bogomips.
Fun :)
(most of this is corporate fileservers, exchange, AD, various crappy apps, network appliances, web servers, SQL servers and idles at around 20% in use). If it all went off you'd need earplugs and fireman's equipment.