TJmax/general temp readings?

BIGBC · 21 Sep 2009 at 12:02

When using temp monitoring apps what should I set the TJmax to ?
On my i7 920 D0 ive left it at 100C.
But with the Q6600 SLACR the thermal specification is 71C, is this a completely different thing ? RealTemp set it to 100C (34/34/28/30) which seems realistic if not a tad over (stock speeds + volts turned down to minimum stable). If i set TJmax to 71C it gives temps of 5/5/-1/1 which is the other end of the scale really.
It was a similar story with my Q9550, guessing the thermal specification has no relevance to the TJmax.

Ive read that the way the temp sensors work they are only really accurate at/around the TJmax anyway.

Im asking more out of curiosity than anything else, computer has been running for ages with no issues.

EDIT: Is the TJmax just used to get the temp reading from the reported delta ? And the thermal specification is what temp it should stay under ?

DIABLO · 21 Sep 2009 at 14:25

Yes it a completly different thing the 71c you're looking at is the overall max for the cpu the overall temp is what you see in the bios and manufacter's monitoring software and is read by a sensor in the cpu socket. The temp given to you by Realtemp for example is the temp of the cores themselves using a thermo diode in the cpu itself and this is the measurement the Tjmax is related too. both i7 and Core 2 both have the Tjmax set at 100c so leave the setting as is.

BIGBC · 21 Sep 2009 at 14:53

So the temp as read by the motherboard is the important one ?
because that seems waaay lower eg
EVGA SLI LE + i7 @4GHz cores around 60 (load) with motherboard sensor reading 22C.
MSI P7N SLI Platinum + Q6600 @stock cores 34/34/28/30 (idle) with motherboard reading 12C.

Do these things need calibrating somehow ?

DIABLO · 21 Sep 2009 at 16:41

You can't calibrate them thats left up to the writer's of the bios and they are notorious for getting it wrong and breaking the temp sensing, thats why people on forums only qoute temps from programs such as Realtemp. The temp read by Realtemp is the important one as it's this that Tjmax is related too and when it reaches 100c the cpu will throttle itself.

Mr Paul · 21 Sep 2009 at 16:55

TJmax is the temperature the CPU manufacture says it will start to throttle at.

TJmax unfortunately isn't well published and it's mainly a "guess", but a well educated guess backed up with rigorous testing without cooling to see what temp they throttle at etc...

The thermal specification is the maximum temperature the heatspreader/mobo CPU temperature can get to before damage will occur.

BIGBC · 21 Sep 2009 at 17:37

So the cores do run considerably warmer than the rest of the CPU, and thats normal. The temperature reported by the motherboard sensor needs to stay below the thermal specification (but has an air of inccauracy) and the cores need to stay below TJmax right ?
Think I get it now cheers.