System Management Bus


System Management Bus

(hardware, protocol)(SMBus, SMB) A simple two-wire bus usedfor communication with low-bandwidth devices on a motherboard,especially power related chips such as a laptop's rechargeablebattery subsystem (see Smart Battery Data). Other devicesmight include temperature sensors and lid switches.

A device can provide manufacturer information, indicate itsmodel/part number, save its state for a suspend event,report different types of errors, accept control parameters,and return status. The SMB is generally not user configurableor accessible.

The bus carries clock, data, and instructions and is based onPhilip's I2C serial bus protocol. Support for SMBus devicesis provided on Windows 2000. Windows 98 does not supportsuch devices.

The PIIX4 chipset provides SMBus functionality. Vendorsusing SMBus would be required to pay royalties.

SMBus website.

Software to interrogate a SMB motherboard.

SMB devices, Part 8 Kernel Mode Driver Design Guide, Win2000 DDK.