But the gigabit ethernet committee started with the requirement of achieving that speed on
existing installed wiring, so they invented a wholly new signalling scheme to do so. They
didn't just overclock fast ethernet and call it a day. Gigabit ethernet barely even resembles
fast ethernet at the electrical level.
Just for starters, gigabit ethernet requires four pairs while fast ethernet requires two.
Gigabit uses five signal levels while fast ethernet uses three. An so forth.