The ASUS Z9NA-D6 motherboard uses a w83795 chip for lm-sensors. Asus provides binary drivers, and then only for CentOS 5.4. On 5.6, you'll need these drivers. I've tested and they work on CentOS 5.6, 2.6.18-238.9.1.el5 x86_64. However, while sensors sees the chip, it doesn't manage to read the values. Must poke at it further.