Who to trust?

[Staz]

I just put together a system for my grandson. An old KT133A chipset based Iwill KK266 (one of the all time great overclocking boards) paired with an AXIA 1GHz TBird (one of the al time great overclocking cpu's) cooled by an SK6 with a whineing delta fan.

With this system I got a cheap thermometer that has 2 probes and fits in a 3 1/2" drive bay. It only reads in F. I trimmed the probe and placed it so that it touches the edge of the cpu core. I also put a smal dab of artic aluminum for better contact. On the MoBo I bent the thermosister up and put a dab of artic aliminum on it also so it contacts the underside of the cpu.

The thermometer reads 124 under full load and he MoBo reports 109 at full load.

Is there really a 15 degree diference between the chip surface and the underside? Is one of them reading wrong? As long as it's stable I really don't care. I was just bored and wanted to hear others opinions as to weather or not we are really 15 degrees closer to the manufactures max temps than we think we are.

Once again this was a very very cheap thermometer that was bought more for astetic vaue than temp monitoring.

[Aedan]

Both probes are probably wrong.

The cheapo one won't have a great accuracy (probably around the 4F or worse mark). The motherboard sensor won't be much better either.

I've found that cheapo thermometers are also affected by things like mains hum and other RF around them. (eg, touching the ground side of the thermometer might make it suddenly read 6-8F lower too)

Net result, who knows which one's accurate. On the other hand, unless you intend to take the CPU up to it's maximum temperature, it's not really a problem!

[Kaitain]

Originally Posted by Staz

Is there really a 15 degree diference between the chip surface and the underside

Yes. In fact there's probably a little bit more of a temperature difference. The ceramic base on T'Birds wasn't that great a conductor. Better than the modern organic substrate, but still not that great, so you will see quite a sharp temperature drop across it. 15ºC is the normal estimate, so if you're seeing 15ºF then you're doing well...