pmbus driver for x86

Hi, My server (S2600CP) has BMC module and power supply with pmbus function. When I try to control and monitor with pmbus driver in linux, it fails. I connected oscilloscope to pmbus connector (SCL, SDA) pins, there was no signal from pmbus driver. But when the system went down, there are pmbus signals which may be generated by BMC. In x86 server, is pmbus connected only to BMC(ipmi)? Is it not connected to CPU i2c bus? is it impossible to monitor power supply with pmbus drvier? Thanks in advance. Regards, J.Hwan Kim