i have a 1ghz transmeta-based tablet that i run it on sometimes. technically it is supposed to be i686-compatible, but doesn’t implement some instructions, so things that target i686 (like linux distros) usually crash very often if they run at all.
haiku often doesn’t like to boot (its an issue with the gpu, i think, netbsd has the same issue on it) but when it does it is functional - anything that isn’t a browser typically runs fine.
i also have a socket 7 motherboard. i was planning to do some work with it today anyway, so out of curiousity i just set it up and tried to install haiku. unfortunately it hangs during boot both with an AMD K5 and a Pentium 133. i might hook up serial and try to figure out the cause later.