Legacy guest OSes typically support OHCI and EHCI. These two controllers are needed because OHCI only handles USB low-speed and full-speed devices (both USB 1.x and 2.0), while EHCI only handles high-speed devices (USB 2.0 only).
Legacy guest OSes typically support OHCI and EHCI. These two controllers are needed because OHCI only handles USB low-speed and full-speed devices (both USB 1.x and 2.0), while EHCI only handles high-speed devices (USB 2.0 only).