The System Management Bus (SMBus), derived from the I2C bus, is a bus system composed of two signals. Intel defined SMBus in 1995, encompassing Clock, Data, and instructions based on the Philips I2C serial bus protocol, with a clock frequency ranging from 10KHz to 100KHz.

Its primary applications include power management, temperature sensors, and EEPROM transmission in laptops.

In laptop applications, SMBus finds widespread use in power management systems. Through SMBus, laptops can effectively monitor and control aspects such as battery status, charging control, and energy management, contributing to enhanced battery life, optimized energy utilization, and ensured system stability.

Moreover, SMBus serves to connect temperature sensors, playing a crucial role in monitoring system temperature in laptops. This allows for fan control or other cooling measures as needed to ensure the system operates within a safe temperature range.

In terms of EEPROM transmission, SMBus provides a serial communication interface for reading and writing data in EEPROM. This functionality is vital for managing and configuring registers, including storing system settings and hardware information.

SMBus employs two main signal lines, SMBCLK (Clock), and SMBDATA (Data). SMBus typically operates at a voltage of 3V, ensuring normal operation while complying with the electrical characteristics and requirements of devices.