Yes, that is interesting. fadd also uses a different port (p5) as compared to SSE/AVX FP stuff which uses p01, so it seems likely that there is separate dedicat

Yes, that is interesting. fadd also uses a different port (p5) as compared to SSE/AVX FP stuff which uses p01, so it seems likely that there is separate dedicated hardware for the x87 stuff, probably in the slice between the main vector pipes and this can also handle the 80 bit stuff.