A8N SLI deluxe PCI Lock

[Hajduk]

I am new to overcloacking and have a question about PCI bus lock. When I start NVIDIA nTune I get a message that my PCI bus is Set to Track HT Bus. So when I increase HT speed the PCI bus will change as well.

Does anybody know how can I lock PCI bus? I looked in a BIOS but was unable to find anything on PCI bus frequency!?

Thanks,