Also see The moonshot that succeeded: How Bing and Azure are using an AI supercomputer in the cloud (Microsoft blog) and A Cloud-Scale Acceleration Architecture (Microsoft Research PDF) for details
"Microsoft’s embrace of programmable chips knowns as FPGAs is well documented. But in a paper released Monday the software and cloud company provided a look into how it has fundamentally changed the economics of delivering hardware as a service thanks to these once-specialty pieces of silicon.How Microsoft Fell Hard for FPGAs
Field programmable gate arrays, or FPGAs, are chips where the logic and networking functions can be reconfigured after they’ve been manufactured. They are typically larger than similarly functioning chips and traditionally were made for small jobs where the performance advantage outweighed the higher engineering cost associated with designing them."