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Motherboard Temp Sensor? Where?

September 27, 2005 at 13:55:56
Specs: WinXP, 3.6Ghz/512

Hi, does everyone know where the motherboard temperature sensor is located? I don't think it is the north bridge is it? I got an Asus P5AD2-E Deluxe Motherboard. Thanks for the help

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#1
September 27, 2005 at 14:54:19

To the best of my knowledge, there is no such thing as a "mother board temp sensor"

There is a CPU temp sensor if that is what you mean... and it's internal to the CPU.


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#2
September 27, 2005 at 16:28:19

There are motherboard sensors. My MB has three of them, one is obviously the CPU, where the other two are I have no idea although I suspect that of them may well be on or near the North Bridge Chip. The third one is probably just sitting on the motherboard somewhere measuring the air temperature within the case.

The three sensors are showing 40C, 30C and 22C. 22C is what you would expect the air temperature in the case to be. There are then two more measuring hard disk temps at 45C and 35C.

Not all CPUs have built in temperature sensors, especially AMD CPUs. With these the CPU temperature is monitored by a thermistor mounted underneath the CPU. The temperature shown by the BIOS is corrected to account for this. If you use a third party application like Motherboard Monitor and an AMD CPU or early Pentium you should take this into account.

PIII on-wards do have an internal temperature sensor.


Stuart


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#3
September 27, 2005 at 17:00:10

A note on temperature sensors. Most sensors are diode junctions embedded in their related chip(s). Very seldom is a discrete thermistor used.

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#4
September 27, 2005 at 19:19:18

OK I guess... No one knows exactly where the motherboard temp comes from. I am just wondering hehe. Thanks anyway guys

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#5
September 28, 2005 at 01:51:30

And for the benefit of Stuart the harddrive temperature sensors are internal to the drives. Not all drives have them.

I used to have a signature but it disappeared and I just couldn't be bothered writing another so please feel free to ingore this.


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#6
September 28, 2005 at 02:48:35

I repeat, There is NO motherboard sensor.

The motherboard contains many different components that operate at several different temperatures so just exactly what do you expect a "motherboard temp sensor" to be sensing???

All modern IC semiconductors come with INTERNAL thermal overload cuircuts (temp sensors) and they are internal to the case of the chip. If they were external to the case then they would be measuring air temp AROUND the chip instead of the actual chip.

There are various chips on the motherboard that have the ability to use the info collected by the thermal overload cuircut and display it for the world to see... the CPU is one of them.


STUART:

Yes, ALL CPU's HAVE INTERNAL TEMP SENSORS. Wizard above is correct... most if not all temp sensors these days are diode based... thermistors are becoming a thing of the past.


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#7
September 28, 2005 at 03:30:22

Not all CPU have internal diodes. If that is what AMD say, I am more inclined to believe them

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/24228.pdf

See Chapter 3. How to measure temperature in system without an on-die thermal diode.

and Chapter 4 Same thing but for systems without an on-board temperature sensor.

One diagram shows you how to attach a thermo-couple to the outside of a CPU.

My motherboard has three thermistors. One sits on the motherboard underneath the CPU, the other is just South of the South bridge in full view for anyone to see it. From the manual verbatim:

"The TCPU1 is used to detect CPU temperature. The TSYS1 is used to detect the system environment temperature."

It may be that thermistors are in the past, but a three your old ABIT KT7A is not part of the past.

BTW. I know that the Hard disk temperature is internal. I just mention hard disk temperatures so that no one would think I was getting confused with motherboard temperatures.


Stuart


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#8
September 28, 2005 at 05:31:30

Stuart:

If you read your document carefully you will discover that the extra diode that you talk about is for READING and DISPLAYING temperature. As I said above SOME chips have the ability to Display their temperatures, some don't.

Operations are a different story... ALL modern semiconductors that have to regulate current or voltage have INTERNAL temp sensors. Even the cheap voltage regulator chips at Radio Shack that sell for $2.00 each.

The reason for this is simple... resistance is an important factor in electronics and resistance changes with heat. In order for the i/o of any regulating or data chip to remain constant, it MUST contain an accurate temperature compensation system. This is especially true with cpu chips because of the wild temp swings that it endures.


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#9
September 28, 2005 at 06:13:30

>> extra diode that you talk about is for READING and DISPLAYING temperature <<

What else would you do with a temperature sensore? And its not a diode, its a Thermistor.

>> ALL modern semiconductors that have to regulate current or voltage have INTERNAL temp sensors.>>

We are getting onto a different thing. Now we are talking about voltage regulators. CPUs arn't voltage regulators but they can and do regulate frequency which is the primary cause of the heat generation in the first place. Thermistors are designed to compensate for changes in resistance due to heat.

While there may be internal temperature sensors, we are talking about temperature sensors that are accessible to the outside world. The P4 has three internal temperature sensors. Only one of them is accessible outside the CPU and is the one that is displayed. The other two are used for throttling the CPU and shutting it down if the temperature gets to high. Something that doesn't exist in AMD CPUs.

But how about this for an Athlon 64.

"All AMD Athlon 64 Processor-In-A-Box packages include thermally controlled fans. A thermally controlled fan detects the current temperature of the processor using a thermistor, and when a lower temperature is detected the fan speed and noise is then reduced. Upon detection of a higher temperature the fan speed is resumed at full speed to appropriately cool the processor."

Hadley an older CPU.

http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_9485_9487^10272,00.html

Stuart


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#10
September 29, 2005 at 02:58:00

What are you talking about???

RESISTANCE generates heat not frequency... frequency is a measurement of time and voltage/current.

And no, we are not "talking about temperature sensors that are accessible to the outside world." The original question asked where the motherboard temp sensor was located.

Your last quote proves the point... They are located INTERNALLY.


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#11
September 29, 2005 at 05:11:33

>> They are located INTERNALLY.<<

Not on AMD CPUs they are not, or are suggesting that AMD are wrong when they devote not one, not two, but three chapters on how to measure temperatures on CPUs without internal sensors.

If frequency has nothing to do with heat in a CPU, why is it that Pentium CPUs have SpeedStep technology that slows them down when they get hot?

Frequency does actually alter the resistance in a circuit. All other things being equal, double the frequency and you halve the resistance. So where does the heat come from?

Why is that 486 CPU didn't have a fan, or at the most, a very small one and 386 CPU didn't even have a heat-sink, not to mention a total lack of internal heat sensors.

"talking about temperature sensors that are accessible to the outside world." The original question asked where the motherboard temp sensor was located.

Yes and my Motherboard has one, accessible to the outside world, not embedded in some components. As stated previously, on the motherboard, right in the path of the airflow from the front fan, miles from any heat generating components. If my motherboard has a sensor measuring air temperature, it is reasonable to assume that there are others as well.

Stuart


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#12
September 29, 2005 at 08:30:36

The relation of frequency and impedance is not necessarily inverse. Only in capacitive circuits. The heating in digital semiconductors occurs mostly in the transition period between on and off. The higher the frequency the greater the portion of time in the transition area.

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#13
September 29, 2005 at 08:55:18

Well it seems I was right, but for the wrong reasons.

I was thinking along the lines of Increase in Frequency = Reduction of Resistance = Increase in Current = Increase in Power Consumption = Increase in heat as the power is dissipated.

Stuart


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#14
September 29, 2005 at 17:53:10

Right for the wrong reasons???? What the heck does that mean??

Stuart you are so far off base now...

CPU chips DON'T have a lot to do with frequency. The frequency stated in spec sheets is the speed of the clock withing the CPU. Other than that, a CPU (simplified) is thousands of tiny off/on switches all syncronized by the clock. The clock itself uses and disipates very little power.

I go back to my original statement with the "mother board temp sensor"... there is none.

A mother board is a printed cuircut board with many different components mounted on it. They all throw off and operate at different temperatures. Just because you have a temp sensor mounted on the mother board doesn't mean it's measuring "mother board temperature" The sensor you're talking about is measuring AIR temperature, and their are several other temp sensors mounted on the board all measuring different things. Should we call these "mother board temp sensors as well???

And yes AS I TOLD YOU, some semiconductors do not have the ability to read and display temperatures and this is what AMD is describing. This does not mean that they do not have internal sensors. It only means that the internal sensors that THEY DO contain are devoted soley to the operation of the CPU and don't have the flashy extra capablity of a display. If a cpu did not have internal heat control they would burn themselves up pretty fast.

Take my words or leave them...


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#15
September 30, 2005 at 05:44:35

>> CPU chips DON'T have a lot to do with frequency. <<

Except that everything that happens inside is CPU is dependant on the input frequency. No input frequency, nothing happens, so heat wont be a problem anymore. Overclock a CPU and it gets hotter.

Tell Wizard Fred that frequency doesn't have a lot to do with CPUs when he says:

>> The heating in digital semiconductors occurs mostly in the transition period between on and off. The higher the frequency the greater the portion of time in the transition area. <<

If the CPU spends an ever increasing time doing something where most of the heat is generated, it is obvious that the result is going to be more heat.

I refuse to believe that any difference in resistance is the sole cause for the increase in temperatures between a 386 and a Pentium 4. Frequency has to be playing a big part and Wizard Fred's explanation makes sense.

>> And yes AS I TOLD YOU, some semiconductors do not have the ability to read and display temperatures and this is what AMD is describing. <<

You implied that the temperature that is displayed in the BIOS, software etc is taken from an internal sensor and thats what we were talking about sensors that are accessible to the user.

>> There are various chips on the motherboard that have the ability to use the info collected by the thermal overload circuit and display it for the world to see... the CPU is one of them. <<

Not AMD CPUs. You made a sweeping statement without qualification along with "thermistors are becoming a thing of the past".

I mentioned the exception of AMD CPUs in my very first post. I stop short of saying all AMD CPUs, but most AMD CPUs need an external thermistor to measure temperature that the user can see.

Now you are being pedantic. Of course the motherboard sensor does not measure the temperature of the actual motherboard which is made of an inert fibre material - any sensible person would realise that. It is so obvious that it goes without saying As I indicated that in my very first post and a subsequent post mentioning environmental temperatures, it's measuring air temperature.

Any reasonable person would have accepted that the motherboard sensor is measuring air temperature and not make sweeping statements like "There is NO motherboard sensor." without qualifying it. If Abit and ASUS and probably other manufactures as well call it a Motherboard sensor, then thats good enough for me. It indicates it is mounted on the motherboard as apposed to in or on a particular componant.

Stuart


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#16
September 30, 2005 at 10:10:19

Look Stuart… You’re not understanding me at all.

First let me tell you that I do this sort of thing for a living. I don’t pretend to know all about computers, but I am an Electronics Engineer and I certainly know how they work.

Let me try to explain it this way… and this is the last time.

ALL cars have temp sensors. They would be crazy not to have them. There must be some way for the motor to tell the driver, or the computer that it is too hot. Some cars have the simple sensors that operate in a simple on/off state controlling a dummy light and some cars have the more expensive sensor that list a temp reading on the dashboard. Regardless to what type they have… ALL cars have them.

CPU’s are the exact same thing… they ALL have internal sensors. It would be crazy NOT to include a sensor within the package. Some have the simple sensor, and some the more expensive sensors that allow you to do flashy things like display temp, control fans…

If you have the less expensive CPU and you want to display temps and other neat things, then you are forced to take the extra step in adding ADDITIONAL sensors to meet the requirements. Obviously you cannot install them internally so you must install them external to the case… and THIS is what your AMD article is describing.

As far as “motherboard temp sensor” is concerned, again, there is none. If you open the newspaper and read that the temp in New York is 70 degrees… it is not. It is ONLY 70 degrees at the point in New York at which the temp is measured. But in actual fact Manhatten is a different temp from the Bronx, which is different from Battery Park, and so on.

The same can be said for a “motherboard temp sensor”. You can have a CPU sensor, a BIOS sensor, a hard drive temp sensor, you can even have an internal computer case temp, but all of this IS NOT SENSING MOTHERBOARD TEMP. The closest thing you can get to a “motherboard Temp sensor” is to measure the air within the computer case and even with that, just like New York, it’s a GENERAL number.

As far as frequency goes… I’m not even going to get into it because you just are not getting it.

I am sorry Stuart, I don’t mean to sound egotistical and I don’t mean to try and make you feel stupid, but this is the simplest way that I can explain.


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#17
September 30, 2005 at 11:14:16

>> IS NOT SENSING MOTHERBOARD TEMP <<

Nobody ever said it did. As I said in my first post, what it is sensing is air temperature.

What we have here is not a lack of understanding of computers, but a lack of understanding of the English language.

Your constant use of unqualified statements leaves the way open to misunderstanding and misinterpretation. Using words like all and unqualified statements like this.

>> There is a CPU temp sensor if that is what you mean... and it's internal to the CPU. <<

The CPU temp sensor that everyone is familiar with is external on AMD CPUs. Whether the AMD CPU has internal sensors is of little interest to most users any more than the names of the internal registers are. I mentioned this in my first post as well.

Considering the the P4 has three temperature sensors, using the singular is misleading.

One thing I do know is that you cannot make sweeping statements where computers are concerned. About the only unqualified statement you can make is that all computers use electricity. After that is all if, but, maybe, sometimes, hardly ever, most and some, but never always and never never.

Stuart


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#18
September 30, 2005 at 13:41:11

Yeah, Okay Stuart... what ever you say.

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#19
October 4, 2005 at 04:42:43

i have a problem with my motherboard temp sensor, i believe it to be broken somehow as my computer keeps shutting down with no warning and the motherboard sensor says the motherboard is up at 110 degrees celcius which is obviously not the case, how can i stop this from happenning preferably without buying a new motherboard as im skint being a student and all if at all possible, this is a fairly major problem as ive got to send this before it shuts down again


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#20
October 4, 2005 at 05:07:53

What does the CPU temperature say? If that is around 110C then yes, that is excessive. If you have a Pentium CPU then they are designed to shut down if things get to hot.

If this problem has just started occurring without you having done anything to the machine like install new hardware then it probably can be fixed.

You need to open the case and look at the heat sink and fan assembly. It will probably be covered in loads a gunk which is what is causing the over-heating.

Remove the heat-sink and give it a good clean. You will need to re-apply heat-sink compound. Here is a good description of how to do that:

http://www.arcticsilver.com/arctic_silver_instructions_big2.htm

Just one more thing. It is normal practise to ask a new question in a new thread. Tagging you question to the end of an old thread can often mean it will only be seen by those that are part of the thread, which in the case of this thread is four people, as apposed the millions that visit computing.net every day.

Stuart


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#21
October 10, 2005 at 16:47:00

My system has a Jetway P4x400DBP motherboard that most definately has a motherboard heat sensor. There is a chip on the motherboard named Winbond that is capable of reading certain sensors. I have downloaded Everrest and the three temperatures it reads are:(1)MOTHERBOARD,(2)CPU, and (3)HDD.
I don't know if this is unique to Jetway or not, but I would think many other motherboards have the same or similar sensing chip on the mobo.

If you find you're going 'round in circles, perhaps you're cutting corners.


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