100mbps/1000mbps over utp

Hi,
Can someone explain how they achieve 100mbps and 1000mbps speed using utp?
They use all the 4 pairs - do they do anything else? Do they acheive these speeds purely thru hardware or do they also tweek the s/w for speed improvement?
Any help appreciated.
- K

IIRC one difference between Cat 3 and Cat 5 is that Cat 5 has more twist per inch. That is, "more twisted"

This should get you what you want.

docs.hp.com/en/784/copper_final.pdf