[jwr]

Oh, these are entirely different approaches. New instructions are something I can use immediately (well, after I get the CPU). I know how to feed data to them, I can debug them, they are predictable, my tools support them, overall — I can make good use of them from day one.

As for FPGAs, anybody who actually used one, especially for more than a toy problem, will tell you that the experience is nowhere near that. Plus, at the moment, we are comparing a solution that could possibly perhaps materialise with something that will simply appear as part of the next CPU.