Actually, the design constraints are quite different. 1. FPGAs have between 1-2 orders of magnitude higher on-chip memory bandwidth. Imagine lighting up all o

Actually, the design constraints are quite different. 1. FPGAs have between 1-2 orders of magnitude higher on-chip memory bandwidth. Imagine lighting up all of the block RAMs on your chip. That blows away the memory performance of a CPU. It's not even close. 2. FPGAs have significantly more parallel compute resources (if your problem isn't purely memory bandwidth limited). Even if it's not stupidly data-parallel, there are several clever design choices you can make to extract a lot of parallelism. It is, as you point out, much harder to program an FPGA. God save me if I have to run SP&R tools again in my life. However, if you have the resources and know what you are doing you will get 10-1000x more performance from an FPGA. Just look at any FCCM paper from the last 20 years. The more apt comparison is FPGAs vs ASSPs. Those are what have been eating FPGA's lunch for the last decade.