Basics of Electricity, Circuits, Transistors, Processors, and CPU Temps

[undefeatedone]

Ok, I'm here to clear this all up, in regards to "Myths and Facts about CPU voltages and heat". Also, I've noticed that people give a lot of advice but rarely any that is based on actual scientific theories or hypotheses tried against the unfailing scientific method.


Basics of Electricity

Volt: A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.

Ampere (Amp): The unit of measurement of electric current. One amp is equal to the electric force of one volt acting across the resistance of one ohm. It is proportional to the quantity of electrons flowing through a conductor past a given point in one second. It is analogous to cubic feet of water flowing per second.

Ohm: The amount of resistance overcome by one volt in causing one ampere to flow. The ohm measure resistance to current flow in electrical circuits.

Any 3 of these Equations work, since they are equivalent algebraically by geometric theorems and postulates.

Volts / Ohms = Amperes
Ohms * Amperes = Volts
Volts / Amperes = Ohms

Example: 1 Volt / 1 Ohm = 1 Ampere
2 Volts / 1 Ohm = 2 Amperes
An electrical circuit with a resistance of 2 Ohms carries 3 amperes of current. What must the Potential Difference (Volts) be?
Do the algebra from here: X Volts / 2 Ohm = 3 Amperes
X/2 = 3
X = 6 Volts. The electrical circuit has a potential difference of 6 volts.

Easy, right? Let's move on to Watts.

Watt: A quantitative measurement of electrical power. One watt equals the power used when one ampere of current flows through an electrical circuit with a potential (electrical pressure) of one volt (Watts = Volts * Amps). They are measure of the work necessary to overcome resistance to the flow of electrons.

Volts * Amperes = Watts
W / A = V
W / V = A

Example: Ok, so a new A64 FX57SD has a Total Designed Power (TDP) of 104W, which means it is designed at stock to run at 110W. We also know the stock voltage is 1.4V. 104W / 1.4V = X amt. of Amperes which works out to be about 74 amps. That means your FX57SD has 74 amps of electrical current running through it in 1 second.


Circuits and Transistors

Source: http://www.faqs.org/docs/Linux-HOWTO...ign-HOWTO.html

Transistors:

"Transistors are miniature electronic switches. They are the building blocks of the microprocessor which is the brain of the computer. Similar to a basic light switch, transistors have two operating positions, on and off. This on/off, or binary functionality of transistors enables the processing of information in a computer.

How a simple electronic switch works:

The only information computers understand are electrical signals that are switched on and off. To comprehend transistors, it is necessary to have an understanding of how a switched electronic circuit works. Switched electronic circuits consist of several parts. One is the circuit pathway where the electrical current flows - typically through a wire. Another is the switch, a device that starts and stops the flow of electrical current by either completing or breaking the circuit's pathway. Transistors have no moving parts and are turned on and off by electrical signals. The on/off switching of transistors facilitates the work performed by microprocessors.

How Transistors handle information:

Something that has only two states, like a transistor, can be referred to as binary. The transistor's on state is represented by a 1 and the off state is represented by a 0. Specific sequences and patterns of 1's and 0's generated by multiple transistors can represent letters, numbers, colors and graphics. This is known as binary notation.

What is a Semi-conductor?

Conductors and insulators :

Many materials, such as most metals, allow electrical current to flow through them. These are known as conductors. Materials that do not allow electrical current to flow through them are called insulators. Pure silicon, the base material of most transistors, is considered a semiconductor because its conductivity can be modulated by the introduction of impurities.

Anatomy of Transistor

Semiconductors and flow of electricity

Adding certain types of impurities to the silicon in a transistor changes its crystalline structure and enhances its ability to conduct electricity. Silicon containing boron impurities is called p-type silicon - p for positive or lacking electrons. Silicon containing phosphorus impurities is called n-type silicon - n for negative or having a majority of free electrons

A Working Transistor

A Working transistor - The On/Off state of Transistor

Transistors consist of three terminals; the source, the gate and the drain.

In the n-type transistor, both the source and the drain are negatively-charged and sit on a positively-charged well of p-silicon.

When positive voltage is applied to the gate, electrons in the p-silicon are attracted to the area under the gate forming an electron channel between the source and the drain.

When positive voltage is applied to the drain, the electrons are pulled from the source to the drain. In this state the transistor is on (data bit of "1", circuit is closed and current flows through the transistor).

If the voltage at the gate is removed, electrons aren't attracted to the area between the source and drain. The pathway is broken and the transistor is turned off (data bit of "0", circuit is open and current does not flow through the transistor) ."


Important Facts

Raising the MHz

Another important fact I have learned: CPU Wattage varies linearly with MHz when there is no change in voltage, therefore, Amperes vary linearly with MHz. Watts = Volts * Amperes. This makes sense because the faster transistors work, the more often they send a signal for a transistor to change (this requires electricity) so they pass more current.


BUT WAIT! UNDEFEATEDONE, we just learned that Amperes = Volts / Ohms! The Volts aren't changing! What about the Ohms? Wouldn't they have to decrease in order for the equation to still be true? Answer: yes, you could say the Ohms technically do decrease! Electricity is passing through the circuits that switch the transistors to "1" or "0" more frequently and therefore more current is passing through the chip. However, this increase in MHz also increases the total power output measured in Watts (V * A = W) because the amperes are increasing and the voltage stays the same. An increase in Watts means an increase in heat output. A closed circuit (one with current passing through it) creates heat because unfortunately it is on a semiconductor and it is creating a bit of friction as it passes through the circuits which is released as heat.

Load Temps - Why Hotter?

Basically the same reason applies to why load temps are higher than idle temps. Think about it. You're changing the transistors on and off a lot more which requires that circuit that turns them on and off to carry a current more. Not to mention the main reason: the transistor is probably switched to the on position for a greater sum of time when you're playing FarCry maxxed out or running SuperPi versus when it's in Standby mode . Remember, current is measured in Amperes, and voltage is staying constant, so when the current increases, watts increase (V * A = W) and temperature increases.

Process Size and Volts

The River That Carries a Current

Q: Why do 90nm processors need less Volts than 130nm, but can handle less also?

A:Think of it like a water turbine on a river. The transistors in the CPU represent the water turbine. Amperes represent the cubic feet of water flowing per second through the river and over the turbine. Voltage is like a huge pump at the beginning of the river that powers the river and affects how fast the water flows. However, you can affect the huge pump at the beginning of the river (voltage on your processor). If you pump up the voltage, you'll get a stronger water current (more amperes). The stonger current you get, the faster your turbine will be able to spin (MHz). However, if the current gets too strong, it will overflow the river (a burnout or a short), or your turbine will break (overloaded transistor). Process size (90nm for example) represents the width of the river. Now a wider river will be able to handle a more powerful pump (130nm will take more volts), but with a wider river you have a bigger turbine, so it will require a more powerful pump. The skinnier river takes a weaker pump (less Volts) and can handle less, but the wider river requires a stronger pump (more Volts) and can handle more.

Temperature also affects this. Remember how resistance is measured in Ohms? The colder a semiconductor gets, the better it conducts (allows current to pass through it, an actual decrease in Ohms) which allows for greater transistor frequency (MHz) and can actually support a higher voltage because a better-cooled transistor is less susceptible to heat damage from increased voltage and current. Cooling a semiconductor is like making the river straighter and making the turbine more sturdy and efficient. Water can flow more easily. It won't splash out as easily (burnout or short) and the turbine (transistor) will be able to handle that increased current and possibly more, with better performance.

Smaller Means Cooler Means Faster

Q: Why can 90nms clock higher, but they don't seem to do much better when supercooled?

A: 90nms can clock higher because they require less voltage and current, so they need less watts and therefore produce less heat. Less heat allows them to run more efficiently than their 130nm counterparts, but when they are both supercooled, temperature difference is minimal, so their efficiency is about equal.


Good info on CPU lifespan versus die temps

source: http://sound.westhost.com/heatsinks.htm

"The reliability and longevity of any semiconductor device is (roughly) inversely proportional to the square of the junction temperature change. Thus halving the junction temperature will result in approximately 4 times the expected life of the component. The converse is also true! A worthwhile increase in reliability and component life can be achieved by a relatively small reduction in operating temperature, since these parameters increase exponentially as temperature is reduced."

The junction applies to the die in this case. You can see how important die temps are to CPU life.

Conclusion:

This article shows there are two major killers of a CPU if you picked up on them: increased current and increased heat. Increased current can overload circuits, burn out transistors, and may create shorts. Increased heat can decrease performance of circuits and transistors, and can also melt them in extreme cases.

Therefore, when Overclocking, to prolong the life of your CPU, since Voltage directly affects the amount of Amperes, keep your Voltage down. Also, keep your computer cooled. Never run at very high temps for prolonged periods as it isn't worth it (decreases the life AND the efficiency of the circuits, which forces you to increase volts to maintain your high clock speed.)

Thanks for taking the time to read this. If you read just the conclusion and believed it, you're obviously a lot smarter. If you had to have proof and read the whole thing, you'll be a true EOCFer and finally know what's behind CPUs and Overclocking!

[FartBubblez]

This shud be given to a Hardware shop =] lol.. good job.. just.. simplify some meanings.. i dun think some ppl can be bothered reading alot of that though

[amdOCer]

it's good, very...... informative =], I agree with FartBubblez, try to simplify some meanings and post more examples about the equations.

[?noob?]

Very well done, not one mistake that I could pick out.
You may want to make it slightly more readable with bolded headings.
Its quite technical and alot of people will be scratching their heads, but if they do some research for themselves, as they **** well should, they should understand the whole lot. Don't bother dumbing it down, to many people expect to be spoon fed.

[butmunch]

Quick glance through, it all seems valid. Maybe it should be stickied?

[enjoidvssk8er]

i somewhat understodd it. all the amps, ohms, volts, watts became mixed up in my head in the end, but i see how it applys to cpu's

[WiCKeD]

I think he dummied it down pretty well.

[undefeatedone]

Yeah, its pretty dumbed down and simplified now.

[?noob?]

Looks good undefeatedone. Alot more readable

EDIT: I vote sticky to

[astrocrep]

Awesome, I have been looking for info like this for a while.

Def a sticky!

-Rich

[GeneStarwind]

Bump for the stickying

[undefeatedone]

Revised it: fixed some minor errors, made it more concise and readable, and added some new interesting sections, such as The River That Carries Current and Smaller Means Cooler Means Faster.

[GeneStarwind]

The River That Carries Current sounds like a movie with some hot chick. Or fruit.

[ether.real]

This is definitely important to understand, however the big question that still remains is, where is the LINE, for each core? Obviously, as each CPU is as unique and beautiful as a hot girl calendar shoot, it wont be 100% the same for every chip. But how do we determine the guideline for vcores and temps? I need some quantification baby!!!

[undefeatedone]

did you read the entire thing? If you did you'll have a lot better understanding.

[ether.real]

sure did. nothing I didnt learn in 2 years of Electronics. All it says is lifetime declines with hi temp and hi volts. Well I already knew that. The question is how much is too much?

[undefeatedone]

Too hard to determine. The margin of error for a motherboard supplying current, how much current gets to the chip, what the chip is made of, how good its resistors, circuits, and transistors are, and how the voltage is read is large. I'd just stick with what's recommended by reviews and established members. Give a detailed scenario and someone will most likely have an identical one. Ask them what temps @ what volts they have, and how stable it is.

[onewecallgod]

i can copy and paste too....
http://www.linuxselfhelp.com/HOWTO/C...n-HOWTO-3.html

[(sin)morpheus]

Doesn't TDP stand for thermal design power and relates to the max heat output rather than the maximum power draw? If you look at iti, if that fx57 is drawing 70+A of current, where the heck is it getting it all from?

edit: woot this is my socket 939 post!

[undefeatedone]

Originally Posted by onewecallgod

i can copy and paste too....
http://www.linuxselfhelp.com/HOWTO/C...n-HOWTO-3.html

Wow, you're a quick one! If you would have read carefully, I cited my resources.

Originally Posted by (sin)morpheus

Doesn't TDP stand for thermal design power and relates to the max heat output rather than the maximum power draw? If you look at iti, if that fx57 is drawing 70+A of current, where the heck is it getting it all from?

edit: woot this is my socket 939 post!

Nope, TDP stands for Total Design Power according to AMD: http://www.amd.com/us-en/Processors/...E13042,00.html

Watts are a measure of power, and power dissipation is directly related to the creation of heat in semiconductors.