The Inquirer saw some new Socket F processors from AMD:
You will notice that the F part has no pins, just flat LGA pads like the LGA775 P4s. In addition, the pads are much more closely spaced than the pins on the 940. Overall size and shape is about the same, but the newer chip has two indents on the top and bottom of the PCB. That PCB is also and organic substrate rather than the ceramic of the older Opterons.
Moving to the top, there are two things to look at, the size and shape of the heatspreader. On 940 parts, the heatspreader goes right to the edge of the package, there is almost no lip, and the walls are flat sided. The Socket F chips have a much smaller spreader with a visible lip of green around the edge, and while very hard to see, it has a stepped effect at the edge of the heatspreader.