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What it is and what it's for
SMC (System Management Controller)
➡️ A small control chip that takes care of:
- power and battery charging,
- fan control,
- the behaviour of the power button,
- sleep modes,
- keyboard backlight,
- power adapter detection.
Reset SMC helps, when:
- MacBook doesn't turn on,
- not responding to charging,
- the fans are running full blast,
- behaves erratically when put to sleep.
PRAM / NVRAM
➡️ The memory that preserves system settings even after the Mac is turned off.
On newer Macs, the designation NVRAM (Non-Volatile RAM), earlier PRAM (RAM parameter).
It imposes e.g.:
- volume settings,
- screen resolution,
- selecting a starter disc,
- time zone,
- some system error conditions.
Resetting NVRAM/PRAM helps, when:
- the Mac isn't booting properly,
- loses sound, video, or starts from the wrong drive,
- brightness, resolution or sound does not work properly.
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How to reset SMC and NVRAM / PRAM
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MacBook with Apple Silicon chip (M1 and later)
- No special procedure is needed - turn off your Mac and turn it back on. If you want to do a „deeper“ reset, turn off the Mac → wait 10 seconds → turn it on. Both SMC and NVRAM are reset automatically on boot.
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MacBook with Intel processor
🔋 Reset
SMC
- Shut down the MacBook.
- Connect the power adapter.
- Hold simultaneously Shift + Control + Option (Alt) + Power at left side of the keyboard.
- Hold for a period of time 10 seconds, then let go.
- Turn on your Mac normally with the power button.
(on a MacBook with a removable battery: turn off → remove the battery → hold Power for 5 sec. → insert back in → turn on)
💾 Reset
NVRAM / PRAM
- Shut down the Mac.
- Turn it on and immediately hold down Option + Command (⌘) + P + R.
- Hold on about 20 seconds (or until you hear the second beep or see the Apple logo reappear).
- After releasing the keys, let the Mac boot normally.
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After resetting NVRAM
Check in System Preferences:
- audio output,
- screen resolution,
- selecting the boot disk, because they can revert to the default values.
