I received my brand new MacBook Pro 2.33GHz Core 2 Duo yesterday and was pleasantly surprised to learn that it runs much cooler than my previous MacBook Pro.
My Core Duo MacBook Pro 2.0GHz (2GB RAM and 160GB hard drive) would frequently reach temperatures of 162° Fahrenheit after running for more than an hour. It would become so hot that it required me to run Fan Control 1.1 if I needed to use my machine anywhere near my lap.
I've been using a new Core 2 Duo MacBook Pro 2.33GHz for over four hours straight (10+ hours on and off) and the temperature hasn't gone higher than 122° Fahrenheit (average is around 115° F) according to CoreDuoTemp - a drop of more than 40° Fahrenheit without using software like Fan Control.
The fans in the C2D MBP come on a little more often and I can hear them changing speed more frequently than they did on my CD MBP, so I'm guessing that Apple made a major adjustment to the System Management Controller (SMC) firmware. The SMC is a micro-controller on the logic board that controls the power functions for the computer. The SMC controls various functions, including:
If you're using a new C2D MacBook Pro, post your CoreDuoTemps in the TalkBack below.
UPDATE: I corrected the headline that previously said that the C2D MBP runs 25 percent cooler. Fahrenheit is not an absolute scale, so percents are meaningless.
UPDATE 2: I left the new MBP running overnight and it maxed out at around 117° Fahrenheit