The TK1 chip have eight on-die thermal sensors and one on-die thermal diode
Seven of the sensors are grouped into three thermal zones,one strongly influenced by the CPU, one strongly influenced by the GPU, and one strongly influenced by the DRAM memory controller and interface, the one remaining sensor plays a support role to the other seven, a hardware controller, called SOC_THERM,can directly read the sensors. The temperature are referred to as CPU_therm,GPU_therm,MEM_therm,PLL_therm.
The TK1 also contain a single, one-die thermal diode that is accessed via an external i2c temperature monitor(Ti TMP451) on Jetson design. The thermal diode temperature is referred to as T_diode.
The same temperature monitor IC(TMP451) used for accessing the thermal diode also contain an internal temperature sensor, whose sensed temperature is referred to as T_board, this temperature that is correlated to the internal PCB temperature and not entirely dominated by TK1 temperature.
MEM refer to the memory controller and interface inside TK1.
PLL refer to the clock domain inside TK1