[stephencanon]

A couple points:

Support for subnormals can easily be disabled (usually be enabling "Flush to Zero" behavior) to allow for better performance on essentially all recent hardware.

Over the last few years, subnormal stalls have shrunk rapidly, and gone away entirely in some cases. Intel started this process with the Sandybridge architecture. These stalls are also greatly reduced in some arm64 implementations.

[ntoronto]

We had this discussion on the Racket user's mailing list a couple of years ago. One user with an AMD processor experienced significant stalls; others with Intel processors didn't.

I don't know the status of AMD's floating point at the moment, but I hope they're doing something about that.