CoolBook is one of those apps you wish you didn't need, but are generally glad you found. If your MacBook or MacBook Pro is running warmer than you are comfortable with and/or you want to squeeze some additional battery life out of it, you can use this software to monitor and change the frequency, voltage and temperature of your CPU. Adjusting the frequency and voltage can dramatically reduce heat dissipation and fan noise. Since you're also lowering power consumption your battery will last longer as well.
CoolBook is shareware and it'll cost you $10. There is a free trial version, but it doesn't allow you to change the voltage/speed settings. Check out the developer's site for some test results and decide if it's for you.
CoolBook makes your MacBook/MacBook Pro cooler
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