Motherboard voltages look wacky

weibullguy · 04-29-2006, 09:48 AM

Well, you peaked my interest and I had to research a few things. According to your lm_sensors output, it looks like you have an ITE IT8712 family integrated circuit (IC). I pulled the datasheet for the IT8712 to see what, exactly, it was. If anyone is interested, the URL is www.ite.com.tw/product_info/file/pc/IT8712F_V0.8.2.pdf. The document is 193 pages. This IT8712 does just about everything. Not that the mobo designers used every feature, but...

The allowable input voltage range to the IT8712 is 0V - 4.096V. Hence, to monitor anything outside this range, you need to use a voltage divider (this is simply two resistors that split the monitored voltage such that 4.096V is the maximum seen at the junction). According to the IT8712 datasheet, the recommended design practice is to select Rb and then calculate the needed value of Ra. ITE recommends an Ra and Rb value between 10,000 ohms and 100,000 ohms.

You would have to know what value Rb was to be able to confidently tweak the /etc/sensors file. But, if you want to try, there are only certain standard values of resistors so those are the only values you need to try. These are 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, and 82. However, you risk masking real problems if you choose wrong.

Now, I issued the sensors -s command on my PC. According to this command, I have no sensors so I'm only assuming the output is a snapshot rather than real-time. One tell-tale sign of a faulty power supply is AC ripple on the output. This ripple will cause the DC voltage to vary up and down around it's true value. The IT8712 doesn't know this is garbage and will report the sum of the actual DC and the ripple. You could take several (10) readings in quick succession and see if the values are relatively constant or bouncing around.

If they're bouncing about, its likely to be cause by ripple. The only option at this point is a new power supply. If they're constant, they may be bad out of the power supply. But if they were truly the values being reported, there would be an acrid odor in your general vicinity by now.

I suspect from my review of the datasheet, that this IC is also controlling your fans. The speed of the fans will be varied based on the temperature readings the IT8712 sees. This is, as I'm sure you know, vital to the health of the mobo components.

BTW, your temp3 sensor is probably not the right type unless you can see frozen parts on your mobo!

onebuck · 04-29-2006, 10:09 AM

Quote:

Originally Posted by BobNutfield

Did some editing in the etc/sensors file and commented/uncommented two entries regarding the it8712 as suggested by Electro. The sensors now look like this:

Code:

it8712-isa-0290
Adapter: ISA adapter
VCore 1:   +1.33 V  (min =  +1.42 V, max =  +1.57 V)   ALARM
VCore 2:   +2.54 V  (min =  +2.40 V, max =  +2.61 V)
+3.3V:     +3.36 V  (min =  +1.57 V, max =  +1.73 V)   ALARM
+5V:       +3.63 V  (min =  +4.76 V, max =  +5.24 V)   ALARM
+12V:     +12.35 V  (min = +11.39 V, max = +12.61 V)
-12V:      -5.39 V  (min = -12.63 V, max = -11.41 V)   ALARM
-5V:       -5.19 V  (min =  -5.26 V, max =  -4.77 V)   ALARM
Stdby:     +4.35 V  (min =  +4.76 V, max =  +5.24 V)   ALARM
VBat:      +4.08 V
fan1:     3183 RPM  (min =    0 RPM, div = 8)
fan2:        0 RPM  (min = 3013 RPM, div = 8)          ALARM
fan3:     2860 RPM  (min = 3013 RPM, div = 8)          ALARM
M/B Temp:    +25°C  (low  =   +15°C, high =   +40°C)   sensor = thermistor
CPU Temp:    +27°C  (low  =   +15°C, high =   +45°C)   sensor = thermistor
Temp3:        -7°C  (low  =   +15°C, high =   +45°C)   sensor = diode
vid:       +0.00 V

A little closer to what they are supposed to be, but still a little wacky. Have no idea what "vid" is, but the instructions said to comment it out with this chip. It also said that with the chip, if the 3.3v readings were 2X normal, to uncomment a variant formula, which I did. This was the result.

Hopefully, this information may help someone else with similar questions.

Thanks,

Bob

Hi,

Bob,you should look here;

http://secure.netroedge.com/~lm78/supported.html

Make sure you have the sensors setup for your MB.

tredegar · 04-29-2006, 11:22 AM

Bob,
If it is any consolation to you, I had big problems with lm_sensors: It kept sending messages to the terminal and my logs saying my CPU was overheating (when I could feel that it was cool), voltages were out of range and the like.
It turned out that it was incorrectly interpreting the data from my motherboard. The prospect of re-calibrating all those variables was not appealing, so I ended up disabling lm_sensors (a year+ ago). No further trouble. Maybe one of these days my CPU will fry, but I think modern ones automatically throttle down / stop when they get too hot.
HTH

BobNutfield · 04-29-2006, 12:34 PM

Hi tredgar,

Yes, that is exactly what my cpu did recently when its fan stopped working and it just shut down. I have the motherboard set to alarm when it reaches 60C. Not really sure what is going on, but the whole thing started when some background script called "beagle-build-in" ran for about 30 mins causing 100% activity in the CPU for this time. The CPU overheated and that is when I decided to try to keep a monitor available and downloaded and installed lm_sensors. But to be honest, I have not found this program to be of much use. Alomost all of the its readings are out, and, as Arow has brilliantly pointed out, some of them are ridiculously absurd. So, I really don't know what use it is going to be to me. I also had my bios set to alarm when the CPU fan stopped working and, even though it was spinning away, lm_sensors set off the alarm and the only way I could stop it was to disable it in the bios. I probably will just dump the program.

Arow, thank you for your efforts. Your knowledge of electrical technology is obviously vast, so I appreciate your input. I built this unit myself about a year a ago, and I am on my third motherboard. When this one goes, as I am sure it will, I believe I will replace it with something else. I will have to study the options. This one is socket 754 and I am hankering for an upgrade to dual core and 939 anyway.

Thanks again for your help.

Bob