I used a tip of sharp carpet-knife to lift the pin carefully from soldered pad while heating it by solder iron. It's clearly visible that those pins was routed to somewhere - they could left them unconnected when only one PS/2 used. I'm just wondering, really wanted to see the schematics...
Just one more detailed photo of the tapped SuperIO:
rayer.g6.cz/hardware/gap67ds3/ps2mod1.jpg
I used a tip of sharp carpet-knife to lift the pin carefully from soldered pad while heating it by solder iron. It's clearly visible that those pins was routed to somewhere - they could left them unconnected when only one PS/2 used. I'm just wondering, really wanted to see the schematics...