This a pilot program of 1,600 servers to test the efficacy of the new system before a decision to roll it out.

I didn't think the system is currently particularly slow at displaying SERPs, but when you think that this is multiplied many, many times a second, fractions are important.

No doubt the energy-saving is really important, too, as that is an ongoing benefit.

Using FPGAs, Microsoft engineers are building a kind of super-search machine network they call Catapult. It’s comprised of 1,632 servers, each one with an Intel Xeon processor and a daughter card that contains the Altera FPGA chip, linked to the Catapault network. The system takes search queries coming from Bing and offloads a lot of the work to the FPGAs, which are custom-programmed for the heavy computational work needed to figure out which webpages results should be displayed in which order. Because Microsoft’s search algorithms require such a mammoth amount of processing, Catapult can bundle the FPGAs into mini-networks of eight chips.Bing To Get "Catapult" Network Architecture To Test Improved Search Speed and Efficiency [wired.com]

The FPGAs are 40 times faster than a CPU at processing Bing’s custom algorithms, Berger says. That doesn’t mean Bing will be 40 times faster–some of the work is still done by those Xeon CPUs–but Microsoft believes the overall system will be twice as fast as Bing’s existing system. Ultimately, this means Microsoft can operate a much greener data center. “Right off the bat we can chop the number of servers that we use in half,” Burger says.

Microsoft's technet post on the topic [blogs.technet.com...]