Slower Version
This makes me think of the -- urban tech legend? -- of some of IBM's various, compatible mainframe computers being "the same" inside, and that when a customer paid for an upgrade to a higher model, a tech would come out, install a jumper, and laze around pretending to work for an hour or two. The advantage to IBM (or any other manufacturer) of such a scheme is having to have only one production line for all of its compatible models across a CPU speed range. The disadvantage to IBM (or other manufacturers) is the customer or some hacker might learn of this, and install a "free" speed upgrade for themselves. These days, if such a scheme exists, it probably involves a BIOS change.
I can't help but wonder if nVIDIA has some magic sauce involving test pins and/or JTAG to enable all the cores, and raise the clock speed, of its chips, thus changing the crippled "export" model into the "regular" model.