The general idea is similar - lots of cores with distributed SRAM memory and some shared DRAM, all sitting on 2D mesh network. The main difference is that Epiphany is made of custom simple RISC cores, while Xeon Phi uses 1st gen Pentiums with huge SIMD FPUs slapped on for higher FP throughput (and TDP).

Interesting.

It looks like (from info on wikipedia pages) the Xeon Phi 3100, gets about 3.3 GFLOPS/WATT, whereas the Epiphany E64G401 manages about 50 GFLOPS/WATT.

So something like 10 of these might compare to 1 xeon phi, and still be cheaper in terms of hardware, and much cheaper in terms of power consumption.

Off the top of my mind (sorry, I don't have the time to double check now):

Phi has shared GDDR and distributed caches. Phi cores and caches are connected through a bidirectional ring interconnect, not a 2D mesh network. Still similar, but not as much.