Crazy k8temp output

BitJam · Posted: Wed Mar 28, 2007 5:24 am Post subject: Crazy k8temp output

I've got an AMD-64 x2 3600+ on an ASUS m2npv-vm mobo. Once I turned on frequency scaling the output from k8temp reads extremely low. For example it is now reading 8C and 11C (around 50F) when the room temperature is at least 65F (18C). When the both cores are running at 100% the temperature reading rises to the mid 30's C (about 90F). I just have the stock heatsink and fan, no refrigeration, so I doubt that the cores are ever below room temperature. I would like to get an accurate temperature reading so I know I'm not frying my CPU. I want to put in a much quieter CPU fan but I am a little leery since I don't know what the actual temperature is. Should I just add 10C to the k8temp readings or is there a better way?

Ironically, one of the it8716-isa-0290 sensors on the motherboard reads extremely high. Under heavy load it can go up the the mid to high 60s C. (about 150F). I've read that this is due to a very hot northbridge and a poor placement of the sensor which puts it right at the power leads to the CPU. I'm planning on replacing the wimpy stock northbridge heatsink with a Zalman ZM-NB47J. But this board has a built-in graphics chip and that heat sink says explicitly that it is not to be used when there is built in graphics chip.

RAIH · Posted: Wed Mar 28, 2007 10:57 am Post subject:

What the

BitJam · Posted: Wed Mar 28, 2007 2:38 pm Post subject:

I just booted up this morning. The room temperature is 65F (18C). Near the floor it may be as low as 15C. Here is the output of sensors:

IQgryn · l33t Joined: 05 Sep 2005 Posts: 764 Location: WI, USA

The CPU and M/B temps at the bottom seem to be working; maybe you should use those instead?

BitJam · Posted: Wed Mar 28, 2007 5:45 pm Post subject:

That was my first thought which caused me to label the sensors as I did. But a little research revealed that both of the it8716 sensors are on the motherboard while the k8temp sensors are actually inside the CPU. The m2npv-vm motherboard I have is peculiar. The sensor I labeled as "CPU Temp" is actually more affected by the hot northbridge and by the power leads to the CPU than it is by the temperature of the CPU itself. The northbridge has a much wider operating temperature than the CPU.

Thankfully, the CPU is much cooler than the northbridge. The heatsink on the CPU is usually cool to the touch. I just don't believe it is below room temperature. Also, it appears that the k8temp sensors are working since the temperature readings go up and down depending in CPU load. I think the problem is that they are not properly calibrated.

robselina · Posted: Wed Mar 28, 2007 10:17 pm Post subject:

you can edit your /etc/sensors.conf file and re-calculate the k8temp values but the calculation will really be a WAG. I ended up doing that for a few sensors on my mobo, I just pulled the values from BIOS before I booted the system a few times and used those to make the output from sensors a little closer to reality. Not the best approach but it's at least a little more accurate.

BitJam · Posted: Wed Mar 28, 2007 11:46 pm Post subject:

Unfortunately the k8temp sensors do not show up in the bios. But maybe I can just measure the temperature of the heat sink and use that to calibrate.

robselina · Posted: Thu Mar 29, 2007 3:24 am Post subject:

BitJam · Posted: Thu Mar 29, 2007 3:38 am Post subject:

Drobbins is from New Mexico.

hvengel · Guru Joined: 19 Sep 2004 Posts: 515

If you go to the arctic silver web site they have a white paper of how to calibrate your CPU temperature reading. It is written for some older Intel CPUs but the basic procedure applies to ANY CPU with an internal temperature sensor and it is fairly easy to do. In most cases where your temperatures are way off there is a constant offset. The procedure on the arctic silver web site will allow you to figure out what this offset is to within 1C. This is more than close enough for your needs.

widan · Posted: Sat Mar 31, 2007 12:56 pm Post subject: Re: Crazy k8temp output

BitJam · Posted: Sat Mar 31, 2007 5:22 pm Post subject:

My stock heat sink looks a lot like the one in the picture. The Zalman is more massive and twice as tall.

The Zalman ZM-NB47J requires mounting holes which my mobo does not have. The stock heatsink is held on by a spring clip. I'm planning to make my own spring clip for the Zalman using this guide. Like the author of the guide, I've been unable to find the right kind of steel wire. My current plan is to use wire from an old coat hanger. I've had the old heat sink off and have verified that the Zalman will fit without needing any dremel tool surgery.

My one remaining concern is that the area where the heat sink makes contact is very small, maybe a quarter inch (7 or 8 mm) on a side. The stock heat sink has a gasket sort of thing shaped like the bezel on a monitor that is maybe half an inch on each side which surrounds the active area. I don't know if it is there to keep dust out or to add physical stability. It is made out of a softish foam material and I don't think I can remove it (for reuse) without destroying it. My current plans are to just ignore it when I attach the new heatsink.