$.$ UHCI$/$OHCI $($USB $1.$x Controllers$)$: These were designed for the original USB $1\mathrm{.}0$ and $1\mathrm{.}1$ specifications, offering low$-$speed $(1\mathrm{.}5$ Mbps$)$ and full$-$speed $(12$ Mbps$)$ data transfers. UHCI $($Universal Host Controller Interface$)$ was developed by Intel, while OHCI $($Open Host Controller Interface$)$ was developed by companies like Compaq, Microsoft, and National Semiconductor. They were the foundation for early USB devices.

$2.$ EHCI $($USB $2\mathrm{.}0$ Controllers$)$: The Enhanced Host Controller Interface $($EHCI$)$ was developed for USB $2\mathrm{.}0,$ which supports high$-$speed data transfers up to $480$ Mbps$.$ EHCI controllers can handle USB $1.$x devices by integrating with UHCI$/$OHCI controllers for backward compatibility.

$3.$ xHCI $($USB $3.$x Controllers$)$: The Extensible Host Controller Interface $($xHCI$)$ was introduced for USB $3\mathrm{.}0$ and later versions $($USB $3\mathrm{.}1$ and $3\mathrm{.}2),$ offering significantly faster data transfer rates $($up to $5$ Gbps for USB $3\mathrm{.}0$ and $10$ Gbps for USB $3\mathrm{.}1).$ These controllers are also backward compatible with older USB standards.