whenever anyone talks about "ARM for the datacenter" ...

... it reminds me of ancient history:

http://www.zdnet.co.uk/news/processors/2001/10/16/arm-to-unveil-64-bit-jaguar-chip-for-handhelds-2097352/

(sorry for cross-linking to non-reg sites)

ARM is great for what they are. To play in the datacenter with the really big guys, we're talking 64bit, terabytes of RAM, dozens of I/O busses. Almost ten year old press releases notwithstanding, ARM hasn't delivered any of that yet.