SMBus

The System Management Bus (SMBus) is a simple two-wire interface wherein basic power-related chips interconnect with other parts of a system, such as within a computer motherboard. SMBus is mostly used in low-bandwidth devices.

Created by Intel in 1995, SMBus was mainly developed to both receive and control data from motherboards in a practical yet highly efficient manner. SMBus is an extremely simple and inexpensive piece of hardware, utilizing analog technology and limited digital capability. The functional design merits simple logic commands.

SMBus technology is based on Philips’ Inter-Integrated Circuit (I²C) serial bus protocol, a multi-master serial computer bus used to connect low-speed peripherals. The SMBus’ clock frequency ranges from 10 kHz to 100 kHz. Its timings and voltage levels are more specific than those of the I²C, although devices from the two different systems operate successfully in the same bus.

An SMBus device can transmit clock and data instructions from the motherboard to the system. Many electronic devices such as the rechargeable battery system of a laptop, a personal computer, and various types of electronics with lid switches and temperature sensors use SMBus.

SMBus can convey specific types of basic data. A device with SMBus can identify the version or model of the device, for example. SMBus also reports errors or events within a system, receives control parameters, and saves and returns its status.

Note that SMBus, even within a desktop or laptop computer, is commonly inaccessible and therefore cannot be configured. SMBus devices are usually unable to identify some of its function details; however, a recent PMBus combination has enableed SMBus to allow that.

SMBus is supported by various Operating Systems such as Linux, Windows 2000, Windows XP, and Windows Vista.

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