apt-get install cpufreqd cpufrequtils
modprobe p4-clockmod
cpufreq-info

cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to linux@brodo.de, please.
analyzing CPU 0:
driver: p4-clockmod
CPUs which need to switch frequency at the same time: 0
hardware limits: 300 MHz - 2.40 GHz
available frequency steps: 300 MHz, 600 MHz, 900 MHz, 1.20 GHz, 1.50 GHz, 1.80 GHz, 2.10 GHz, 2.40 GHz
available cpufreq governors: ondemand, performance
current policy: frequency should be within 600 MHz and 1.50 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 600 MHz (asserted by call to hardware).

processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping : 4
cpu MHz : 600.000
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm up
bogomips : 4815.22

p4-clockmod