Introduction / Why This Is Needed
SMC (System Management Controller) is a microcontroller on a Mac's motherboard responsible for low-level management of power, fan operation, keyboard backlighting, battery status, sleep (hibernation) function, and many other hardware features.
Over time, SMC settings can become corrupted due to software glitches or hardware issues. This manifests as:
- Unusually high fan speeds under light load.
- Battery charging problems or rapid discharge.
- Incorrect operation of indicators (e.g., keyboard backlighting).
- Problems entering sleep mode or waking up.
- Issues with USB port power (on some models).
SMC reset (SMC reset) is a standard diagnostic and recovery procedure that forcibly reboots the controller, restoring its settings to factory defaults. It does not delete your personal data, macOS settings, or installed applications.
Requirements / Preparation
Before you begin, ensure:
- Your Mac is connected to power if it is a notebook (MacBook, MacBook Pro, MacBook Air). The procedure requires stable power.
- All unsaved documents are saved. The procedure will cause a system reboot.
- You have correctly identified your Mac's architecture (Apple Silicon or Intel), as the methods differ significantly.
Step-by-Step Instructions
For Macs with Apple Silicon Processors (M1, M2, M3 and newer)
On Apple Silicon-based Macs, the SMC is part of the system-on-a-chip (SoC), and its reset is performed differently than on Intel.
- Completely shut down your Mac. Click the Apple logo → "Shut Down". Wait for it to power off completely (screen is black, no backlight, fans have stopped).
- Wait 30 seconds. This is a crucial step to discharge power circuits.
- Disconnect all peripheral devices (monitor, flash drives, external disks, mouse/keyboard, except the power cable).
- Turn on your Mac normally (by pressing the power button).
- After the system boots, you can reconnect the peripherals.
💡 Tip: If the issue persists, try a full cycle: shut down Mac → unplug power cable for 30 seconds → plug back in and turn on.
For Macs with Intel Processors
Here, the methods depend on the type of enclosure (notebook or desktop) and presence of an internal battery.
Option A: MacBook (notebook) with a non-removable battery (all models from 2010 onward)
This is the most common scenario.
- Connect your MacBook to power using its power adapter.
- Shut down your Mac. Apple menu → "Shut Down".
- Press and hold simultaneously the keys:
Shift (⇧)+Control (⌃)+Option (⌥)(left of the spacebar)- And the power button.
- Hold all four keys and the button for 10 seconds.
- Release all keys and the button.
- Press the power button to turn on your Mac.
Option B: MacBook with a removable battery (very old models, up to ~2010)
- Shut down your Mac.
- Remove the battery.
- Press and hold the power button for 5 seconds.
- Reinstall the battery and turn on your Mac.
Option C: Desktop Macs (iMac, Mac mini, Mac Pro)
- Shut down your Mac. Apple menu → "Shut Down".
- Unplug the power cable from the wall outlet (or power supply) for 15 seconds.
- Plug the power cable back in.
- Wait a few seconds, then turn on your Mac.
⚠️ Important: For iMacs (especially with a flat screen), it may take ~30 seconds after unplugging power for capacitors to fully discharge. Be prepared that the first boot after this procedure may take longer than usual.
Verifying the Result
After macOS successfully boots, check if the original symptoms have disappeared:
- For fan problems: Boot the system and open "Activity Monitor" (
/Applications/Utilities/Activity Monitor). "Energy" tab. Fan speeds should be normal (typically 1000-2000 RPM at idle). - For charging problems: Check the charging indicator in the menu bar or in "System Settings → Battery". The Mac should correctly display the charge level and status.
- For sleep problems: Try to put the Mac to sleep (Apple menu → "Sleep") and wake it. Ensure the transition is smooth, without freezes.
- For USB problems: Connect an external drive or other device. It should be recognized by the system.
If symptoms have not disappeared or new ones appear, the problem may be hardware-related (e.g., a failed battery or temperature sensor). In this case, contact Apple Support or an authorized service center.
Potential Issues
| Symptom / Error | Probable Cause | Solution |
|---|---|---|
| Mac won't turn on after SMC reset (notebook) | Battery fully drained. The reset procedure may have caused a slight "loss" of charge. | Connect the MacBook to power and leave it for at least 15-20 minutes without attempting to turn it on. Then press the power button again. |
| Fans run at maximum immediately after reset | This is a temporary effect. The SMC is recalculating all parameters (temperature, load). | Let the system idle for 5-10 minutes. Speeds should stabilize. If not — check CPU load in Activity Monitor. |
| macOS reinstallation required on Apple Silicon after reset | Extremely rare, usually related to corrupted system files, not the SMC. | If the system doesn't boot, try booting into Recovery Mode (hold the power button until options appear) and use "Reinstall macOS". |
| USB power issues persist | The SMC handles USB on some models, but the problem could be in the ports themselves or the controller. | Try resetting NVRAM/PRAM (see related article). If that doesn't help — hardware diagnostics. |
| Unsure which method to use for my model | Incorrectly identified Mac type (especially between old Intel and new Apple Silicon). | Double-check your model in "About This Mac". If the name contains "M1", "M2", "M3" — it's Apple Silicon. If it says "Intel Core" — it's Intel. |
Note for Users of Older Macs (pre-2016)
On very old Mac models (e.g., MacBook Pro before 2012, Mac mini before 2014), SMC reset algorithms may differ slightly. If you have such a model and the standard instructions didn't work, find your exact model (e.g., MacBookPro11,2) and refer to Apple's official article HT204463 ("Reset the system management controller (SMC) on your Mac"). The general principles (power disconnection, key combinations) remain the same.