Asus P5K-VM + e6550 + Ultra 120 extreme = Temps below ambient

[Kari]

I recently build a new rig for my parents with following specs:

mobo: Asus P5K-VM G33 mATX
cpu: e6550 (at stock)
mem: Corsair twin2x2048-5400c4 (2x1G)
hdd: Seagate barracuda 7200.10 320GB
case: Antec Sonata III
cpucooler: Ultra-120 Extreme with Scythe S-Flex 120mm fan
windows xp sp2

So, the problem is I'm getting idle temp readings that are below ambient, and SpeedFan, Core Temp, TAT and BIOS show similar readings, maybe one or two degrees difference..
From SpeedFan 4.32
System: 34C
Cpu: 14C
HD0: 38
Core 0: 20C
Core 1: 19C

ambient is around 26-27C, It's been nice and warm here in Finland for couple of days

With original bios (ver. 0304) the cpu temp was ~10 degrees higher, (around 25C) so it was even higher than the core readings at that time (core readings are same before and after the bios upgrade), after I updated the bios to version 0401 I get those readings above and there is still obviously something wrong with them.

At full load with TAT:
CPU 0: 34C
CPU 1: 32C

So theres about 15 degrees difference between idle and load, wich seems ok
There seems to be an offset of some sorts but how much is it and is there a way to fix it??
And is it caused by the mobo or is the cpu's sensors faulty?

 

[Kari]

On another forum one fellow thinks that those temps are being misread as quadcore cpus which use a 100-DTS instead of dualcore cpus which use 85-DTS, so he thinks the actual temps are 15C higher than those readings..
Is he right? I want a second opinion 😉

 

[nukemaster]

yup some software that does not know about the Thermal-Junction being 100 and not 85 will result in a temperature being 15c too low. after all 20c is near imposable(full imposable with your ambient temps).

You can try speedfan with a 15c offset and see if its more accurate.

I know my quad was reading 15 too low so i just did that.

 

[Kari]

You can try speedfan with a 15c offset and see if its more accurate.

yeah, For sure the temps will look more reasonable with the offset but there isn't really a way to tell if its more accurate or not
But maybe thats a good assumption to make in this case...

What do you think, is it possible to fix something like this with a new bios version? so far the latest didn't but Im hoping the next one will.

 

[nukemaster]

http://www.thecoolest.zerobrains.com/CoreTemp/ <--Core Temp

This is almost the most accurate way to read temps.

Just so you know speedfan is 15c lower only due to the fact that it does not account for the fact that the new cpus have a 100c thermal junction

when speedfan had the update(to even support core2), all (core2)cpus had a t junction or 85.
so speed fan goes how far off my t-junction and I and the cpus says 50 and speed fan goes ok 85-50=35 and returns 35c.
For real it should be doing 100-50=50. So the 15c offset just makes it go 85-50+15=50 so you get the right temp.

It should also be noted that core2's and A64's(even the original 754 ones) come with internal temp sensors that are accurate within 1c where as before you have to place a sensor in the socket and hope it was calibrated close to what it should be. from what i can see most motherboard utilities(because they read this socket sensor, even most core2 and a64 boards still do this) where off by as much as 20c so old cpus saying 50 where closer to 70c in the core. so 60c on a dual or quad core aint all that bad when you think of it

Hope this clears it up a bit more

 

[dragonsprayer]

readings are wrong unless your misting the system

only be something like the evaporation of water can it be lower then ambient