PC Hardware in a Nutshell, 3rd Edition

USB HCI Types

There are three types of USB host controller:

Open Host Controller Interface (OHCI)

The Open Host Controller Interface (OHCI) is a USB 1.X interface that was developed by a consortium of PC makers led by Compaq, Microsoft, and National Semiconductor. OHCI places more of the burden for managing USB functions on hardware, and less on software. OHCI is most common in systems that use non-Intel chipsets, including those from ALi, SiS, and VIA. Windows 98/SE/Me and Windows 2000/XP include native OHCI drivers. You can download the full Open Host Controller Interface Specification from http://h18000.www1.hp.com/productinfo/development/openhci.html.

Tip

If you run Windows 98SE on a system with an OCHI, visit the Microsoft web site and read Knowledge Base article 253697. This combination of OS and HCI can cause some very odd behavior, such as unplugging a bulk-mode device from one root hub port causing a hub connected to a different root hub port to disconnect. One possible symptom, believe it or not, is your computer making a high-pitched whining noise, like a phaser about to self-destruct.

Universal Host Controller Interface (UHCI)

The Universal Host Controller Interface (UHCI) is a USB 1.X interface that was developed by Intel. UHCI places more of the burden for managing USB functions on software, and less on hardware. UHCI is most common in systems with Intel chipsets, although many non-Intel chipsets also use UHCI. USB devices designed to use UHCI (e.g., the Intel ...