The mystery of the mini USB type-B connector has been solved: it’s likely to be a separate way that ZOTAC uses to have its overclocking software monitor the SMBUS components.
This is quite peculiar of ZOTAC as the SMBUS can usually be read by the means of the driver interface, but there’s still the fact that NVIDIA sometimes blocks access to some components they decide are too sensitive to let their partners meddle with.
This way ZOTAC’s Firestorm OC software has a more direct way to monitor the video card.
ZOTAC is touting the possibility that their Extreme Edition of GeForce GTX 680
will reach even 2 GHz, but that will probably happen only if lots of conditions concur: you get lucky and stumble upon an extremely capable GPU sample, you do have extreme cooling solutions for the card, you happen to have exceptional overclocker skills and so on.
But, for now, there’s a video on Expreview
that shows the card has already reached 1400 MHz.