They don't advertise 939 Opteron support except on boards specifically intended to be in the same market (like the few Tyan 939 boards that exist) *but* pretty much any 939 motherboard on the market will fully support Opterons out of the box nowadays. Providing it supports Venice/San Diego cores it'll work with single core Opterons and the same is true if it supports dual cores (it'll work with dual core Opterons).
14x and 15x are single core San Diego.
16x, 17x and 18x are dual core Toledo.
Just look for that in the CPU support list.