This is a list of the voltage "notches":
0.925 (some 480's can run stock clocks at this voltage)
0.938
0.950
0.963 (GTX 480 idle voltage)
0.975
0.987 (load voltage of most reference 480's)
1.000 (load voltage of some reference 480's)
1.013 (as above)
1.025 (as above)
1.038 (as above)
1.050 (as above)
1.063 (as above, this is the highest I've seen, EVGA)
1.075 (some factory overclocked cards have this voltage, eg: Gigabyte SOC)
1.088 (as above)
1.100
1.113
1.125
1.138 (max voltage available by default in Afterburner, you can go higher though)
This list also applies to the GTX 470; however I don't know the idle/load voltage that most reference 470's ship with.
