thermal paste issue?

[tecknical]

I noticed something lately. Whenever I check my MBP's temperature readings from iStat Menu, the GPU diode is always 10C higher than the GPU heatsink. Do you think this is caused by bad thermal paste application or is it normal?

Also, my MBP is still in warranty (July 07) so I don't want to take it apart and reapply the thermal paste. Do you think if I take it to the apple store and show them the issue they'll reapply the thermal paste or do I just have to wait until I'm out of the warranty.

 

[J the Ninja]

Think about this one for a second. The heatsink and diode would only match if the heatsink and chip package were a perfect conductor of heat, and even then only if ALL the chip's heat energy went into the heatsink metal (some goes into the board, etc), AND none was disapated between the die and the heatsink sensor. Which seems unlikely considering we just established the heatsink's thermal conductivity is in the the "hypothetically flawless" range. There's gonna be a difference. The fact that one exists and is 10C doesn't tell you too much about the thermal paste, unless you have some frame of reference.


Also, have you ever done thermal paste application before? If so, ignore the rest of my post. If not, I'd recommend you don't try it for the first time on the MBP. Practice on another machine before doing it on your MBP, as the heatsink is a pain to get on and off. Getting the right amount of paste is tricky until you get a bit of practice at it. If do decide to give it a go, I'd recommend one of these two:

http://www.newegg.com/Product/Product.aspx?Item=N82E16835202006&Tpk=OCZ freeze

http://www.newegg.com/Product/Product.aspx?Item=N82E16835186020&Tpk=arctic MX-2

 

[eldy]

iStat doesn't give accurate absolute readings anyway. our c2d processors will shut down automatically at 105C but iStat gives readings above that.