Rudster816
Well its the electrons that determine temp. So Im assuming the maximum tempeture is when those start moving at the speed of light. 
The electrons do travel at around the speed of light in a good conductor.
It's how hard they are pushed (voltage) through a restriction (resistance) which causes heat, not how fast they travel.
They always travel the same speed in the same conductor/circuit in the same conditions. Increasing the CPU speed does not cause the electrons to move faster. Increasing the CPU speed just increases the frequency of the logical on-off cycle. Higher frequency equals more cycles per given time. All the while, the electricity never changes speed to a noticeable extent. Increasing CPU frequency changes how fast the electricity is allowed to pulsate between different electrical potentials, not how fast the electricity moves.
EDIT: Alright, the speed of electricity does change. I didn't want to confuse you and say it NEVER changes. It just doesn't change in this application by a noticeable amount. The speed of electricity is different through different conductors and different depending on the temperature of the conductor, the density of the conductor, and other atmospheric conditions -- including atmospheric pressure to a small extent. But these changes in electrical speed are not what you are referring to.
In the application we are referring to (CPU), the change in electrical speed is negligible.
So how can we control the CPU's heat (other than cooling)? We have no control over the CPU's internal resistance and the conductors utilized. The only thing we really have control over (other than cooling) is the CPU voltage, CPU speed, and CPU load. More voltage will create more heat because it will push the electrons harder through the resistance and therefore increase the current. Higher CPU speed will make heat go up also -- even if the voltage is left the same. The transistors in the CPU which act as logical switches require some electricity just for their operation. So, the transistor will consume a bit more power than what it is providing for the load. The faster the the transistor frequency, the more often it will need voltage provided to it to excite it to logical on state as needed. And by the same token, as CPU load is increased, more transistors will be switching back and forth between logical on and off states (instead of a certain percent just idling along at a logical off state) since more computational power will be needed and therefore more power will be consumed and more heat produced.