What causes overclocked machines to run unstable?

Is it the heat? If you could keep the components cool could you just keep running up the clock speeds?

or something else?

Bad memory timings, or most likely lack of voltage to memory or in most cases CPU. I'm currently fighting with the same problem and I'm really not happy that I need enormous amounts of voltage going to my CPU to get it Prime95 stable.

However, keep in mind, more voltage always means more heat and the increase is greater the higher the voltage.

can be many things

Heat is not good
A bad chip...
bad motherboard

Most common reasons are heat (relating closely to voltage) and other components becoming unstable, such as the chipset, RAM, etc.

Yea, heat and lack of voltage are the main culprits....in years past, I've seen mainboards submerged in liquid nitrogen to get it to wild speeds, but the boards were modified for extra volts and fsb's

I would imagine its as much an inability of the materials involved, even assuming (improperly) that there are absolutely no defects, to handle the transactions fast enough.

The transitor has to switch on or off. The material used in that transistor determines how quickly that charge can be started or stopped.

By increasing the voltage and the GTLREFs you can push it faster by moving the range of charge/discharge to a faster portion or an increase in the sensitivity to voltage differences.

I could be way off though.

Methal said:

Is it the heat? If you could keep the components cool could you just keep running up the clock speeds?

or something else?

Click to expand...

Physics basics 101:
W = V x A
Where W = watts, V = volts, and A = amps. As you increse voltage you increase wattage or total energy going to the CPU. Some of that energy is transformed into heat. As you increase the energy the percentage that gets changed into heat also increases.

Heat causes an increasing amount of the energy to leak out of the pathways that are the circuits of the CPU. Heat also causes a decrease in electrical conduction; more resistence and more heat.

Heat is your enemy.

Assuming the ability to cool the CPU to -20 centigrade versus air cooling, then to some degree cooling allows greater frequencies to be achieved both because you can pump more volts into the CPU (without heat effects) and you have greater conductivity (less resistance) because you are running at temperatures below zero degrees centigrade, which reduces electrical leakage over CPUs running at 60 degrees centigrade.

As to voltages, everythng else being equal, higher voltages allows higher frequencies. There is a certain minimum voltage required for which ever CPU you are concerned with to achieve a certain frequency.

As you raise the clock frequency the capacitance in the circuits start limiting
the voltage levels of the signals. The more you raise the clock the lower the signal voltage till it gets so low that it goes below the logic circuit threshold level.

Which is why raising the voltage works