Why does mbm show my cpu temp to be 7 degrees lower than my case temp?

[Ymmy]

i have a biostar m7ncd and the latest motherboard monitor shows my cpu to be 5-7 degrees lower than my case. is it possible for the cpu to be cooler than the case? i am using alx800 with a case fan on my barton 2800. the case has 1 fan blowing into it.

 

[Connoisseur]

wow I have almost the same exact mobo, cpu and HS. I'm running a mobile barton at 2.4 ghz and my case temp NEVER goes below 43C even when the AC in my small room is at full blast. I suspect that the case temp diode can't go lower than a certain temp. Also, make sure that your CPU temp monitor and your case temp monitor aren't reversed. MBM does this frequently. I'm assuming that's what's wrong. it makes sense that a cpu temp would be 5-7 degrees HIGHER than case temp.

 

[Sonic587]

Nope, it's not possible to get below ambient temps with just air cooling. You're motherboard/CPU is giving you FUD. It's not a problem, though. Temps can vary a LOT from MB to MB.

 

[Cerb]

What does your BIOS say? It's not uncommon for MBM's settings to be wrong. Do a little Prime95, RC5 or SETI and see how they go.

 

[dmw16]

You may also have the wrong diodes selected within mbm...obviously something isnt quite right.

 

[Ymmy]

my bios says the same as mbm. plus mbm has their own thingy where all you do is put in the name of the mobo. so i couldn't have possibly messed up the settings.

 

[Cerb]

Originally posted by: Ymmy
my bios says the same as mbm. plus mbm has their own thingy where all you do is put in the name of the mobo. so i couldn't have possibly messed up the settings.

I believe you on the BIOS, but no, you could still have messed up. MBM's little setup wizard is not perfect.
But if the BIOS says that, then there's something else going on. Odd.

 

[piasabird]

I have seen some power supplys that make more heat than a CPU. The drives all make heat also.

 

[Mo0o]

Yeah, my cpu is always cooler than my case as well

 

[Cerb]

Originally posted by: piasabird
I have seen some power supplys that make more heat than a CPU. The drives all make heat also.

More heat than the CPU? unless it's powering an old SCSI RAID array, that's insane (current PSUs should be 65-80% efficient, nearing or breaching 80% at optimum load).
However, the ehat from the HDDs, video card, and other parts is in the cool air going to the CPU. So the CPU reading being cooler is impossible, unless a) the sensor is set up wrong or damaged or b) the sensor is just below, above or beside the CPU, such that it gets the hot air from the CPU heatsink.

 

[Ymmy]

poo, does anyone have this mobo?

 

[Connoisseur]

Ymmy I have this same mobo. Like I posted before I still have the same problem with my case temp never going below 43C when the room temp is damn near freezing (50F). My CPU temp also never went down below 36C even when I had the cpu running at 1.66 ghz @ 1.35W (this is a mobile 35W barton 2200+). The cpu should be MUCH cooler than this. I seriously think the winbond sensor can't go below a certain temp or is overreading the temperatures. I want to know how to calibrate this to fix it.

 

[fr]

If your CPU is idle and has a fan cooling it, I don't see why it couldn't be cooler than the ambient case temp.

 

[Cerb]

Originally posted by: fr
If your CPU is idle and has a fan cooling it, I don't see why it couldn't be cooler than the ambient case temp.

Somebody needs to take high school physics.
W/o TEC, you cannot make the source of heat colder than that which is used to cool it down.

 

[fr]

Originally posted by: Cerb

Originally posted by: fr
If your CPU is idle and has a fan cooling it, I don't see why it couldn't be cooler than the ambient case temp.

Somebody needs to take high school physics.
W/o TEC, you cannot make the source of heat colder than that which is used to cool it down.

Yes, but there can be other things producing heat in the case other than the CPU like hard drives, a graphics card, or the power supply.

 

[MichaelD]

Originally posted by: dmw16
You may also have the wrong diodes selected within mbm...obviously something isnt quite right.

My thoughts exactly.

 

[Cerb]

Originally posted by: fr

Originally posted by: Cerb

Originally posted by: fr
If your CPU is idle and has a fan cooling it, I don't see why it couldn't be cooler than the ambient case temp.

Somebody needs to take high school physics.
W/o TEC, you cannot make the source of heat colder than that which is used to cool it down.

Yes, but there can be other things producing heat in the case other than the CPU like hard drives, a graphics card, or the power supply.

But guess what? This is an ATX case.
HDDs heat the air first, then video and ICs on the mobo, and then that hot air cools the CPU, and exits the case. The PSU generates heat and exhausts it, but in doing so, becomes null and void for measuring temps within the case.

 

[VirtualLarry]

Originally posted by: Cerb
But guess what? This is an ATX case.
HDDs heat the air first, then video and ICs on the mobo, and then that hot air cools the CPU, and exits the case. The PSU generates heat and exhausts it, but in doing so, becomes null and void for measuring temps within the case.

Yep. That's the way that my mid-tower case is set up. I have three HDs in the lower front, with an intake fan actively cooling them. The bottom and top HD of the stack both have temp sensors, bottom reads 34C, top reads 38C. (Which is kind of strange, because at times there is usually only 1C diff between the two.) Anyways, the case ambient temp (right now) is also 38C. (That temp went up a bit, ~2C, since I added my passively-cooled ATI Radeon 9200 AGP card to the case.) The CPU temp reads 49C, which is between 10-12C above case ambient, which I consider acceptable. Before I cleaned out my CPU fans and re-applied the thermal grease, that was closer to 15-18C above case ambient, which I consider too much. (AMD XP2000 CPU, 166MHz x 10.0, 1.52v) I don't run any sort of CPU-idle/cooler program, and I have all BIOS power-management stuff disabled as well, so that temp is mostly "full load", although it can go up again another 2C running Prime95 or games. I consider anything under 55C to be acceptable for this range of CPU.

If your mobo's temp sensors don't reflect this rough general pattern (intake 34C, case ambient 38C, CPU 49C), then either the sensors are mis-labled, or otherwise incorrect. CPU temp should definately NOT be lower than case ambient temps. This commonly occurs when MBM has the sensors backwards, I've seen it before. That "wizard" thing that it uses, depends on user reports, and sometimes they are wrong, or don't apply correctly to different revisions of the same board.