Wierd CPU Temp Behaviour

[ironique]

I have this wierd issue with my A64. When I boot my PC in the evening when I get home from work, my CPU idles at 40C and hits 55C on load. The wierd thing is, if I restart the PC once or twice, my idle temp goes down to 34C and load temps drop to around 50C? Can anyone explain this behaviour? I use a Zalman 7700Cu with the thermal paste that came with it.

 

[Doctorweir]

hmmm...interesting. I know the cooler is good, but that good...
What tool do you use for temp readout?

Just one curious side note: What Voltage is your RAM at?

 

[ironique]

I use speedFan for temps, and Everest too. They report the same temps. Vdimm = 2.75v

 

[Jotho]

Originally posted by: ironique
if I restart the PC once or twice

Bingo! I'm glad to hear I'm not the only person experiencing this behaviour. I'm using the K8N Neo Platinum (s754) and experience exactly the same behaviour with stock CPU cooling. On first boot, I idle at about 44-45, with max load being 53-54. After a reboot, I idle at 38 and my max load never passes 48. I'm assuming it's a MSI-only feature...

 

[ironique]

bump

 

[clarkey01]

Originally posted by: ironique
I have this wierd issue with my A64. When I boot my PC in the evening when I get home from work, my CPU idles at 40C and hits 55C on load. The wierd thing is, if I restart the PC once or twice, my idle temp goes down to 34C and load temps drop to around 50C? Can anyone explain this behaviour? I use a Zalman 7700Cu with the thermal paste that came with it.

The coolers fine......Im stumped

You gotta love these A64's, full of surpirses !

 

[yliu]

The behavior you see is completely normal. The motherboard uses an internal algorithm to derive the CPU temperature from the reading of the CPU thermal diode, which involving adding an internal offset to the read out. This internal offset often change from reboot to reboot. To calculate your real CPU temp, you can read http://www.silentpcreview.com/article191-page1.html

Personally, I use this formula to estimate my CPU temp:

Load temp: (Load temp - idle temp) / 0.9 + ambient temp in case
Idle temp: (load temp - idle temp) / 0.9 * 0.1 + ambient temp in case

This formula relies on the fact that the load and idle temps use the same offset and thus their difference would eliminate the effect of the changing offset. I believe for most boards the difference in temp is much more accurate than the absolute reading.

I then divide this number by 0.9 because for winchesters the power at idle is roughly 10% of the power at load. Then the rise in temperature should account for 90% of the power, so dividing by 0.9 will give you the rise over ambient at load.

 

[soulraver]

Just update your mobo bios and everything work fine.

 

[yliu]

Don't know about other neo2 owners but I've tried every bios from 1.36B to 1.51B on mine and they all have the same temp problem.

 

[MrControversial]

Originally posted by: ironique
I use speedFan for temps, and Everest too. They report the same temps. Vdimm = 2.75v

Speenfan is kinda iffy. I stopped using it after it wouldn't read anything above 33C. Try using the monitor that came with your mobo if possible.

 

[htaddict]

After reseating my Zalman 7000 heatsink and reapplying the AS5 due to what I thought was wildly fluctuating temps, I discovered the following:

The MSI K8N Neo2 has a known problem measuring the CPU temperature. Problem still exists on the latest released BIOS (1.5)

When the system boots the BIOS does a calibration of sorts on the temperature probe for the CPU. When you do the first cold boot (thermally cold that is) of the day, the cold calibration has tendency to cause the system to report higher temperatures. Many people have seen that the difference between a thermally cold boot and a warm boot is 10 deg C.

Meaning, if you boot cold the CPU temp will report 10 deg C hotter than if you reboot and the CPU is warmed up.

This offset is calibrated by the system only once during boot up and remains unchanged until you boot again. Apparently the design of the temperature diode in the Athlon 64 can be problematic to read/calibrate. Other boards and manufacturers apparently have had problems but have patched the problem with an updated BIOS (either fixed the problem or hid it).

After many google searches and searching on the MSI Forum, I found a utility that someone created that can read the temperature offset as well as set it.

I have found for my system the difference is 6 deg C on average.

I created a batch file to log to a csv file every time my system boots to record date and time along with the offset. On a cold boot the offset would be in the 60-63 deg C range (typically 61). On a warm boot the offset would be in the 51-57 degree range (typically 56).

I decided to set my offset to 56 deg C every time my system boots.

Here is a sample from the log I created (last column added manually for reference):


Date Time Offset Boot Condition
--------- ----------- ------ --------------
2/28/2005 9:14 AM 61 Cold
2/28/2005 10:54 AM 61 Cold
2/28/2005 11:02 AM 58 Warm
2/28/2005 11:07 AM 56 Warm
2/28/2005 12:02 PM 55 Warm
2/28/2005 12:27 PM 53 Warm
2/28/2005 12:43 PM 53 Warm
2/28/2005 12:44 PM 56 Warm
2/28/2005 1:59 PM 56 Warm
2/28/2005 2:11 PM 55 Warm
2/28/2005 2:17 PM 57 Warm
2/28/2005 2:23 PM 56 Warm
3/1/2005 2:50 PM 62 Cold
3/1/2005 5:26 PM 60 Cold
3/1/2005 7:58 PM 56 Warm
3/1/2005 10:09 PM 57 Warm
3/1/2005 11:43 PM 56 Warm
3/1/2005 11:45 PM 57 Warm
3/1/2005 11:48 PM 57 Warm
3/1/2005 11:55 PM 57 Warm
3/1/2005 11:58 PM 57 Warm
3/2/2005 12:02 AM 57 Warm
3/2/2005 12:13 AM 56 Warm
3/2/2005 12:16 AM 56 Warm
3/2/2005 12:22 AM 56 Warm


Let me know if anyone wants the utility and/or the batch file I created to log to a csv file.

Speed Fan works fine on the MSI K8N Neo2 Platinum. The MSI Core Cell utility has been known to cause system crashes if left running in the system tray.

 

[Amaroque]

Originally posted by: Jotho

Originally posted by: ironique
if I restart the PC once or twice

Bingo! I'm glad to hear I'm not the only person experiencing this behaviour. I'm using the K8N Neo Platinum (s754) and experience exactly the same behaviour with stock CPU cooling. On first boot, I idle at about 44-45, with max load being 53-54. After a reboot, I idle at 38 and my max load never passes 48. I'm assuming it's a MSI-only feature...

I've noticed this. The temp sensor on the Neo2 seem to be subjective, not absolute. I'm also running the latest BIOS. I was experimenting, and ducted outside air on the CPU bringing it down to about 20c full load. While the CPU was still very cold, I rebooted, the BIOS reported 48c. It's not an A64 problem, it's a MB problem, as my ASUS K8N does not behave like this.

I posted a thread about this IIRC in early January, and got no replies.

 

[Jotho]

Originally posted by: Amaroque
I'm also running the latest BIOS.

I'm running v1.4 on my mobo right now. I wondered if flashing to 1.5 might fix the problem. It doesn't bother me a whole lot since i know it's inaccurate, but it'd be nice if it worked all the same.

 

[Amaroque]

Originally posted by: Jotho

Originally posted by: Amaroque
I'm also running the latest BIOS.

I'm running v1.4 on my mobo right now. I wondered if flashing to 1.5 might fix the problem. It doesn't bother me a whole lot since i know it's inaccurate, but it'd be nice if it worked all the same.

Nope, it didn't do anything for this problem. I'm thinking it's an inherent MB problem that cannot be fixed w/o replacing the MB.

This is very annoying, and concerning. I tested my theory more, and found out that I can basically make the MB say whatever temperature I want it to. If you have the CPU hot (I unplugged the CPU fan, and ran Prime95) and reboot with the fan on, it will come up as at like 30c when you reboot windows. If you cool the CPU way down, take the extra cooling off, and then reboot, it will say it's running at like 65c in windows.

 

[ironique]

Originally posted by: htaddict

Let me know if anyone wants the utility and/or the batch file I created to log to a csv file.

I'd like the utility. Is it small enough to attach to an email? I could PM you my email address.

Is there absolutely no way to find out the actual CPU temperature on the Neo2 Plat? This is really disturbing. For a mobo that OC's so well, temperature monitoring should be pretty important!