Overclocking Radeon in Ubuntu

This is a dump of aticonfig. Forgive the formatting.

ATI Overdrive (TM) options:
The following options are used to get and set current and peak, core
and memory clock information as well as read the current temperature of
adapters. By using the "--adapter=" argument the ATI Overdrive (TM)
options can be targeted to a particular adapter in a multi-adapter scenario.
If no adapter is explicitly targeted the commands will be run on the Default
adapter as indicated by the "--list-adapters" command
--od-enable
Unlocks the ability to change core or memory clock values by
acknowledging that you have read and understood the ATI Overdrive (TM)
disclaimer and accept responsibility for and recognize the potential
dangers posed to your hardware by changing the default core or memory
clocks
--od-disable
Disables ATI Overdrive(TM) set related aticonfig options. Previously
commited core and memory clock values will remain, but will not be set
on X Server restart.
--odgc, --od-getclocks
Lists various information regarding current core and memory clock
settings.
Including: current and peak clocks
the theoretical range clocks can be set to
the current load on the GPU
--odsc, --od-setclocks={NewCoreClock|0, NewMemoryClock|0}
Sets the core and memory clock to the values specified in MHz
The new clock values must be within the theoretical ranges provided
by --od-getclocks. If a 0 is passed as either the NewCoreClock or
NewMemoryClock it will retain the previous value and not be changed.
There is no guarantee that the attempted clock values will succeed
even if they lay inside the theoretical range. These newly set
clock values will revert to the default values if they are not
committed using

Source: foreverrising.wordpress.com