L7's to give you a desired voltage. details inside :)

[el]

AMD Athlon Thunderbird, Duron overclocking voltage table.
1.850
I I I I I .
1.750
I I . I I .
1.650
I . I I I .
1.825
I I I I . .
1.725
I I . I . .
1.625
I . I I . .
1.800
I I I . I .
1.700
I I . . I .
1.600
I . I . I .
1.775
I I I . . .
1.675
I I . . . .
1.575
I . I . . .

[pik33]

Duron default: | : | : | . (1.6V)
After penciling: | | | : | . (1.8V)

You can also get 1.85V (all penciled) or 1.65 V ( | : | | | . - may be too low)

It was enough for my Duron to always boot up to 1 GHz