TJmax/general temp readings?

[BIGBC]

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 ?

 

[BIGBC]

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 ?

 

[BIGBC]

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.