why increase CPU voltage when OCing?

[themajorrager]

so why is it that i have to increase the CPU voltage when i OC?
i am running my Venice 64 3500+ @ 2.53G - with 1.47V... it has been running fine using superpi and temp never got above 46C.
mobo is Asus A8N-SLI. im leaving the RAM alone for the moment as i tried it before and it cracked the shits...

 

[theteamaqua]

some how by doing that u can OC more, its like more power cos , P=IV , i think lol, increase voltage > incraese power, and higher clock speed tends to use more power, i think

 

[Bobthelost]

Increasing the voltage makes the transistors (think tiny switches) inside the CPU turn on and off faster. This means that you can increase the clock speed further.

 

[Ketchup]

Originally posted by: Bobthelost
Increasing the voltage makes the transistors (think tiny switches) inside the CPU turn on and off faster. This means that you can increase the clock speed further.

Your answer is the closest so far. When you give you CPU more voltage, the transistors turn on and off more forcefully, thus allowing you to raise the clock speed. Think of it as opening and closing a door. The faster you do it, the more force you need to use to get the door completely open and completely closed.

 

[imported_ST]

when you raise the clock frequency, setup and hold timings are affected on the rising and falling edge; if raised too high, your system will be unstable beause it violates these parameters. With increased voltage, you gain some timing window, since you require less time to go to the proper logic levels.

 

[Jeff7181]

Originally posted by: ST
when you raise the clock frequency, setup and hold timings are affected on the rising and falling edge; if raised too high, your system will be unstable beause it violates these parameters. With increased voltage, you gain some timing window, since you require less time to go to the proper logic levels.

Translation... when you switch a transistor faster and faster, you need to increase the voltage (aka, electrical pressure) to allow the transistor to "charge" adequately and be considered ON. Otherwise the transistor is switched off before a high enough voltage rise is seen on the other side and the transistor remains OFF.

Think of it like holding a cup under a faucet sideways, this is the OFF position. To turn it ON, you turn the cup rightside up. The frequency at which you turn the cup is like the clock frequency of the CPU. Whether the glass is full or not is whether the transistor is actually producing an ON or OFF signal (a 1 or a 0). In order to fill the cup while turning it faster, you need more water flow... either by opening the faucet more (more amperage) or by increasing the water pressure (more voltage). Since we can't open the faucet more (more amperage), we increase the pressure (voltage).

The downside to this is that it increases current leakage within the CPU. Using my previous analogy, this would be the water that runs down the side of the glass when it's in the OFF position. While it's not nearly that severe with a CPU (current flow doesn't remain the same when the transistor is in the OFF position as in the ON position) it still exists and increasing electrical pressure makes it worse.

*EDIT* By the way, I know it's not a perfect analogy, but it should give you a basic idea of what's going on and why increasing voltage helps increase the stability when clock speeds are increased.

 

[Munky]

Well, before we get into all these analogies, I should mention that you should only use higher voltage if you need it to make the overclock stable. Increased voltage will shorten the lifespan of your cpu, even if the temps are low. There's no exact telling how long it will last - it may still last much longer than you plan to keep the cpu, but with increased voltage there's always a higher chance of it dying early - be it 6 years or 6 months from now.

 

[dmens]

Originally posted by: ST
when you raise the clock frequency, setup and hold timings are affected on the rising and falling edge; if raised too high, your system will be unstable beause it violates these parameters. With increased voltage, you gain some timing window, since you require less time to go to the proper logic levels.

Changing the cycle time does not affect setup/hold times (not significantly anyways), those checks are primarily set by circuit topology on a given process. But yes, increasing voltage will give critical paths more time to meet the given timing checks, since gates have increased current drive and signal slopes become crisper (faster propagation).