So you have a Mac, it’s acting funny, and it seems to be something hardware-related. Reset the SMC / NVRAM!
Wait, What’s the SMC?
SMC stands for System Management Controller, a critical low-level component on Mac hardware. Much like the name sounds, the SMC controls and managements system hardware for power consumption, battery charging and battery function, thermal activity and fan activity, LED lighting for keyboards and displays, GPU functionality with video mode changes and video output, sleep and wake, and other core hardware functionality on a Mac.
Keep in mind that by resetting the SMC you will lose power specific settings, like the time it takes to sleep a Mac and other customizations to power settings. No big deal, but if you have made many changes to your hardware behavior you will want to adjust stuff like sleep behavior again. The boot time after resetting a machines SMC can be a bit longer than usual, that is normal.
Ok, What is NVRAM / PRAM?
Volatile RAM), which used to be called PRAM (Parameter RAM) holds assorted information about your Mac so that it functions to your specifications. In no particular order, here are some things stored in NVRAM:
Virtual Memory (commonly called swap)
Video and display information including monitor depth, refresh rate, screen resolution, and number of colors
Volume for both system startup and speaker
Time zone information
Mouse and trackpad scaling and speed information (commonly called mouse acceleration)
Keyboard repeat rate
Kernel Panic information
DVD region settings
Default system fonts
When you reset the NVRAM, this information gets cleared out of the Mac. Because of the information stored in NVRAM, if you reset it you’ll often have to readjust things like your mouse tracking speed, time zone (if it’s not set to an online server), and any non-native resolution that any attached display is running.
Resetting the SMC:
MacBook Pro, Air, Retina
– Hold down the Shift+Control+Option+Power keys at the same time.
– The little light on the MagSafe adapter may change colors briefly to indicate the SMC has reset.
– Boot your Mac as usual.
iMac, Mac Pro, Mac Mini
– Disconnect the power cord
– Hold power button for 5 seconds
– Release the button
– Reattach the power cables and boot the Mac as usual
Resetting the NVRAM/PRAM:
– Reboot the Mac and then immediately hold Command+Option+P+R. You must hit the key combination before the grey screen appears otherwise it won’t work, you may need to try it once or twice until you get the timing right.
– You will then hear the Mac reboot sound again, signifying that the Macs PRAM has been reset successfully.