The PowerPC architecture includes a 64-bit TimeBase register, which is logically divided into 32-bit upper and lower fields (TBU and TBL). The TimeBase register is incremented at a frequency that is hardware- and software-implementation dependent and may vary from time to time. Transforming the values from TimeBase into seconds is a more complex task than in the POWER architecture. To obtain time values in PowerPC systems, use the read_real_time() and time_base_to_time() interfaces.