socket 939 or 754 mobo?

i was looking through milwaukee pc by me and they have a board that has memory slots for both chipsets, and sockets, but it says on the box to only install one chip at a time. Has anyone heard of this before and is there any potential there?

These arnt SMP machines, simply hybrids.

They allow you to run either or, not both...and they do it slowly at that.