Your argument is that this is the only difference. If so, then Tenstorrent should have chosen x86. They could support all the way through SSE3 without patent n

Your argument is that this is the only difference. If so, then Tenstorrent should have chosen x86. They could support all the way through SSE3 without patent negotiations and maintain backward compatibility rather than risking it on a new ISA. Why didn't they? The same reason that software devs don't want to implement a bad API that's been continually updated for years. A new API allows you a chance to do things better even if both APIs technically do the same exact things. You can move quickly and confidently spending that mental energy and time on things like performance instead of contemplating weird edge cases and writing endless tests for each of them. The same applies to Tenstorrent and RISC-V. The cleaner ISA means you don't have to sit around thinking about how an instruction can be potentially executed for a weird side effect and how that will propagate through the pipeline. Instead, you can focus that mental energy on performance enhancing changes. In any case though, Intel sells 6-7x more chips than AMD, so even with 2x the people, their economies of scale are still better. That said, I believe a cleanroom RISC-V design by Intel would still progress faster at Intel than x86 does and it would probably require fewer people allowing them to put the rest on other projects and the overall reduction in team size might even further increase the design rate (as you've stated).