Innovation of the 10 Gigabit Ethernet Task Force. XAUI (pronounced "Zowie") is a ten Gigabit/second interface. The "AUI" portion is borrowed from the Ethernet Attachment Unit Interface. The "X" represents the Roman numeral for ten and implies ten gigabits
Crystal clock oscillator (XCO): An oscillator that relies on a crystal for its frequency reference. A piezoelectric crystal oscillates at a very stable frequency.
