This is a lost post from my early blogs around 2012, rediscovered and posted here in mid-2020
If you are using Linux and the pm-utils suite from freedesktop.org to manage resume/suspend, and the chances are you are since most distros use it, then you could benefit from reading a recent post on my other blog .
Pm-utils’ implementation on CPU governor and CPU frequency is broken. If you use the userspace governor with a custom frequency, the frequency does not get restored on resume.
What does this all mean? When you close your laptop’s lid, the machine is put into suspend, or sleep. The current governor is saved. Next time you open the lid, the governor is restored, but the custom frequency is not restored.
I use a custom frequency to slow down my laptop on hot days when it tends to overheat. Read the post for a simple fix so that the frequency gets saved and restored along with the governor.
(Manual frequency management can be problematic. You don’t want to slow the CPU down so much that it is working harder on average, because that will generate more heat. You need to find the fine line between wasting high frequency and heat, and working too hard that adds heat. But that is a topic for another day.)
 [Ed: 2020, lost now]