a question about p4_clockmod module on Xeon quad core processors

[Xiaoning Ding]

Has anyone tried the p4-clockmod module to scale frequencies of Xeon quad-core processors? 

I have 2 Xeon 5355 processors and want to scale down their frequencies for some experiments. I have tried the acpi-cpufreq module. But it can only scale down the frequence from 2.67GHz to 2GHz. Does anyone have experience with the p4-clockmod module to get even lower frequencies with Xeon quad core processors?

Thanks!

Xiaoning