Reset SMC/NVRAM

Every Intel Mac contains two components that manage system configuration: NVRAM and the SMC. NVRAM (non-volatile random-access memory) stores settings including startup disk selection, screen resolution, time zone and sound volume. (Older Macs use PRAM, or parameter random-access memory.) If you have persistent problems with any of these, NVRAM is something to suspect.

The SMC (system management controller governs the system’s response to the power button (or opening or closing a MacBook), battery and heat management, the ambient light sensor (used by the display’s auto-brightness feature), keyboard backlighting, indicator lights and external video input on select iMacs.

Resetting NVRAM or the SMC shouldn’t be necessary, and it’s not something you should do unless you have a good reason, but most experienced Mac users will have seen it fix unexplained glitches and it won’t harm your Mac.

To reset NVRAM, power on your Mac and hold å+ç+P+R immediately, and keep them held until the Mac finishes starting up, sometimes restarting itself again during the process. Refer to bit.ly/ mfrstnv for more details.

To reset the SMC on any desktop Mac except an iMac Pro, shut down the Mac (using  > Shut Down – don’t just put it to sleep), physically disconnect the power cable from the Mac, wait 15 seconds, plug it in again, wait five seconds, then press the power button to start up the Mac. Don’t worry, there’s some leeway in the timings. It’s slightly more complicated for MacBooks: see bit.ly/mfrstsmc for steps for portable Macs and the iMac Pro.