your'e right when you say 'they aren't locked', but thats also true even for the lowest core i7-9xx parts. the point is that the westmere(-ex)s have a lowest multi of 12 (regardless of processor type/number) AND they have a highest multi, which in case you haven't an extreme edition cpu, is exactly the multi they are rated at (including turbo bins of course) and changing the multi is allowed only in that range! so only extreme edition cpus are allowed to overclock via multi and as far as i know there aren't any xeon extreme edition parts (yet?)!
