They started from a new clean-sheet design. You can read about it here: https://en.wikipedia.org/wiki/Zen_(microarchitecture) https://en.wikipedia.org/wiki/Zen_

They started from a new clean-sheet design. You can read about it here: https://en.wikipedia.org/wiki/Zen_(microarchitecture) https://en.wikipedia.org/wiki/Zen_(microarchitecture)