I doubt that FPGA performance/perwatt,same 28nm, FPGA can only get 5x lower power，14nm GPU is more efficient，so it can be 4x
The VU9P FPGA is a 16nm device, not 28nm.
Yes of course. I thought LTCMAXMYR compares 1080ti with 28 nm FPGA.
i have some parameters，2015 some FPGA miner mine MAXCOIN （as you see, my nick name have a MAX)
keccak 2 core ,@200MHz，may run 300Mhz,but Limited by chip specification and board 1.0V DC/DC power.
28nm kintex 325t, 400M, 25W , ~2.1A @12V, so 16M/W
same time GeForceGTX970 got 400M @125W , 3.2M/W
xilinx report 16nm 2x improvment
https://www.xilinx.com/products/technology/power.html16nm XCVU9P may get 32M/W
16nm GTX1080ti ,1200M, 150W ，8M/W
that is about 4x
14nm GPU will be more efficient，so it can be lower than 4x
1080ti makes 30mh with 150W which is 0.2Mh/W which is x20 more efficient.