Sometimes the Scaling Maximum Frequency of a CPU is reduced below that of the possible top frequency and finding out why this is can be problematic. The limitation could have been imposed by:
* Thermal limits
* Hardware limitations (e.g. ACPI _PPC object).
* Program that wrote to a /sys/devices/cpu/cpu*/cpufreq/scaling_max_freq
Fortunately Thomas Renninger introduced /sys/devices/cpu*/cpufreq/bios_limit that exports to user space the BIOS limited maximum frequency for each CPU. This feature is available in Ubuntu Maverick 10.10 upwards.
So, if you have a machine that you believe should have CPUs running at a higher frequency, inspect the bios_limit files to see if the BIOS is mis-configured.