Translations:Kernel/Gentoo Kernel Configuration Guide/48/en

Most systems will come with two of the above interface types: EHCI (USB 2.0), plus either UHCI or OHCI (USB 1.1). It is important that you select both types present on your system. While all USB 2.0 devices are backwards compatible with USB 1.1, a large proportion of USB devices (even the ones being manufactured today) are based on the USB 1.1 interface - why would a USB mouse need more than 1.5Mb/s?