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Why cant we boot at high voltages?

post #1 of 10
Thread Starter 
Out of curiosity, why will a cpu not work when it is running at a voltage that is to high?

And beyond this why does temperature affect our maximum voltage?

For example at 60c I can not boot a cpu at 1.7v, but at 30c i can. Why is this?
At 30c I also get a better frequency at 1.6v then i do at 1.7v.

Technical terms are fine, actually I would appreciate a scientific approach.

Thanks!

FYI, i know these arnt safe voltages. Im in for the science and am working with ln2 to keep temperatures where i want em.

Cheers
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post #2 of 10
High voltages causes cpu to raised its temperature in the process of gaining heat. It depends what cpu you used varies different type of manufacture, stepping and model.

Frankly speaking, as long as you stay below the limit of your cpu's temperature, voltages and other settings it should be alright.
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post #3 of 10
Quote:
Originally Posted by OverShocked View Post
Out of curiosity, why will a cpu not work when it is running at a voltage that is to high?

And beyond this why does temperature affect our maximum voltage?

For example at 60c I can not boot a cpu at 1.7v, but at 30c i can. Why is this?
At 30c I also get a better frequency at 1.6v then i do at 1.7v.

Technical terms are fine, actually I would appreciate a scientific approach.

Thanks!

FYI, i know these arnt safe voltages. Im in for the science and am working with ln2 to keep temperatures where i want em.

Cheers
What exactly are you asking?

Why wont it boot at high voltages at high frequencies?
    
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post #4 of 10
Electricity is energy, and the higher the energy, the higher the heat (ex. to break up ionically bonded compounds, you need a lot of HEAT, aka energy). The problem is, there's a certain point at which electrical components cannot take all of that heat without just plain failing. The cause of this is quantum tunneling. You hear this term thrown around a lot, and it sounds fancy, but quantum tunneling is quite simple: when something that shouldn't be able to cross a certain block, is able to cross it. In this case, the electricity's kinetic energy overcomes the block's or barrier's potential energy, thereby crossing it, which you can imagine is going to cause a large amount of problems. The electricity going through a chip needs to go through set, definite paths, leading to set logic gates, thereby executing a set action. If it can cross into different paths, things are going to get mis-calculated, 0's are going to change to 1's, and vice versa.
The conclusion being, the lower the temperature, the lower the chance of quantum tunneling as the electricity's kinetic energy will be kept in check; however, no matter how low the temperature, there comes a point when too much energy is too much and quantum tunneling will occur no matter what.
Edited by crazyap7 - 1/22/11 at 7:42pm
post #5 of 10
Thread Starter 
Quote:
Originally Posted by MR KROGOTH View Post
What exactly are you asking?

Why wont it boot at high voltages at high frequencies?
Kind of...

Maybe it would help if you saw my correlation of temperatures and frequencies.

I am more asking why will the system not boot at a specific voltage that is to high?
Crazyap7 managed to answer this very well though.



Second, I am asking why in my results do I see a massive difference in the frequencies attained when the CPU was at 1.7v as the temperature dropped and 1.2v.



For example, as you can see from my graph the line of the system at 1.2v almost falls off as the temperature goes down. But at 1.7v we see a massive difference in frequency as temperature goes down.
Edited by OverShocked - 1/22/11 at 8:39pm
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post #6 of 10
Thread Starter 
Quote:
Originally Posted by crazyap7 View Post
Electricity is energy, and the higher the energy, the higher the heat (ex. to break up ionically bonded compounds, you need a lot of HEAT, aka energy). The problem is, there's a certain point at which electrical components cannot take all of that heat without just plain failing. The cause of this is quantum tunneling. You hear this term thrown around a lot, and it sounds fancy, but quantum tunneling is quite simple: when something that shouldn't be able to cross a certain block, is able to cross it. In this case, the electricity's kinetic energy overcomes the block's or barrier's potential energy, thereby crossing it, which you can imagine is going to cause a large amount of problems. The electricity going through a chip needs to go through set, definite paths, leading to set logic gates, thereby executing a set action. If it can cross into different paths, things are going to get mis-calculated, 0's are going to change to 1's, and vice versa.
The conclusion being, the lower the temperature, the lower the chance of quantum tunneling as the electricity's kinetic energy will be kept in check; however, no matter how low the temperature, there comes a point when too much energy is too much and quantum tunneling will occur no matter what.
Thanks a ton!! This answers my first question very well. Would you mind looking at my second question in the post above?

Thanks!
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post #7 of 10
So if I understand correctly, you're asking why is it that at 1.2v, no matter the temperature, you're not going to go much higher ~3.7GHz-4.0GHz, but when at 1.7v, you can go anywhere from 4.3GHz to 6.0GHz?

Well, while I can't really be 100% sure of the answer to this question, I can hypothesize that 1.2v is really too small an amount of energy to run your processor at anything higher than 4GHz. No matter the temperature, 1.2v will not lead to quantum tunneling, and it will not provide the energy needed to run your processor at anything higher than 4GHz. As you can imagine, 1.7v is a HUGE jump, and it's going to provide a lot more energy to do just about anything the chip wants. When it's not cooled enough though, that high amount of energy is going to lead to quantum tunneling, which'll make the chip fail. The more the chip is cooled, the higher you'll be able to go without the chip shutting down because of the electricity's kinetic energy exceeding the barrier's potential energy.
In short, 1.7v will give the chip a lot of energy, but it won't be able to max out the chip's potential without the chip shutting down first, unless you have appropriate cooling.
post #8 of 10
Thread Starter 
Thanks for your response again.

Im sorry, but its somewhat hard to explain what I am asking. I am rather asking why we see such a large drop off in the low voltages (1.2-1.3v). For these voltages, a lowering in temperature makes very little affect beyond about 0c.

While when we look at 1.5v, 1.6v and 1.7v it scales very well all the way down to -90c. Meaning that we still see fairly large frequency bumps for every drop in temperature.
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post #9 of 10
I would guess that it's because 1.2v-1.3v just isn't enough energy to go anywhere with, all you can do with it is go lower. You start seeing a difference when the amount of energy going in exceeds what you can max your processor out with at a certain temperature. Say, for example, that your processor needs exactly 1.5v to run at 5GHz, but only if the temperature is -10*C. So if the temperature is 10*C, 1.5v will not get you 5GHz, but once you lower the temperature, it will. Conversely, assume the maximum frequency 1.2v can run is 4GHz. No matter what the temperature, it'll still be 4GHz.
post #10 of 10
Heat increases resistance and decreases the capacity of a conductor to carry current. At 1.7v you are likely causing more localized heating that increases resistance more than the increased voltage can compensate for. It's like accelerating so quickly that your tires spin, instead of moving the vehicle.

At least that is my layman's hypothesis. Ask an electrical engineer if it makes sense.
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