The Sideband Temperature Sensor Interface (SB-TSI) is a digital serial interface to temperature sensors integrated on AMD microprocessors. It allows microcontrollers on the motherboard to monitor the processor temperature and adjust cooling solutions accordingly.
SB-TSI was first implemented on processors of the x86 CPU Family 10h, augmenting and later replacing pins which provide direct access to an integrated thermal diode. Modern processors can have a larger number of thermal sensors in strategic locations on the chip(s), monitored by an integrated microcontroller, the system management unit, so SB-TSI reports an average temperature.
SB-TSI emulates a typical remote temperature sensor chip which samples the analog signal from a thermal diode and has various control registers and registers to read out the current temperature and alert status. The temperature is provided in increments of 0.125 °C from 0 to 255.875 °C. This is Tctl, the control temperature, which is normalized for all processors such that 100 °C is the maximum permitted temperature. A model specific offset to the physical temperature is also reported. SB-TSI can optionally assert the ALERT signal, active low, to notify motherboard logic if the current temperature exceeds a programmable upper or lower threshold.
SB-TSI implements a subset of the SMBus protocol and shares the sideband interface of the processor with other integrated remote management devices. Processor Family and Model specific details are documented in the respective "BIOS and Kernel Developer’s Guide" (BKDG), or for newer processors the "Processor Programming Reference" (PPR).
- "SB Temperature Sensor Interface (SB-TSI) Specification", AMD Publ. #40821, Rev. 1.62, August 2010