Troubleshooting a malfunctioning Mac often involves standard steps like restarting, using Disk Utility, or performing a Safe Boot. However, resetting the NVRAM (Non-Volatile Random-Access Memory) or SMC (System Management Controller) can resolve more elusive issues. These instructions apply to Intel-based Macs; M-series Macs lack an SMC and NVRAM reset procedure (though a simple shutdown and restart is often sufficient).

Understanding PRAM and NVRAM:

Historically, clearing PRAM (Parameter RAM) was a common fix. PRAM, a small battery-backed memory, stored crucial startup information. Modern Macs use NVRAM, which serves a similar purpose but stores fewer settings: startup disk, volume, resolution, time zone, and kernel panic details.

When to Reset NVRAM:

Consider resetting NVRAM if settings repeatedly revert, screen resolution or volume are inconsistent, or the date/time is inaccurate. This is a quick, harmless procedure.

Is Resetting NVRAM Safe?

Yes, it's safe, but it resets settings to factory defaults. You may need to reconfigure custom settings afterward.

How to Reset NVRAM:

M-series Macs: The system automatically checks and resets NVRAM if needed. A simple shutdown and restart is recommended.

Intel Macs:

1. Shut down your Mac.
2. Press the power button and immediately hold Command-Option-P-R.
3. Hold for about 20 seconds (or until a second startup chime on older Macs).
4. Release and let your Mac boot normally. Check System Preferences (Startup Disk, Display, Date & Time) to verify settings.

Troubleshooting NVRAM Reset:

A gray screen after holding the keys might indicate a USB device conflict. Disconnect all USB devices (except a wired keyboard), shut down completely, then try again. If using a Bluetooth keyboard, try a wired one.

Terminal Method (Advanced Users):

While generally unnecessary, advanced users can use the Terminal command nvram -c followed by a restart. Use caution with Terminal commands.

Understanding and Resetting the SMC:

The SMC manages power, temperature, fans, lights, and keyboard backlights. A faulty SMC can cause excessive fan noise, slow performance, charging issues, or sleep/wake problems.

When to Reset the SMC:

Reset the SMC if you experience any of the aforementioned SMC-related issues.

Is Resetting the SMC Safe?

Yes, it's safe. Check your Battery preferences after the reset.

How to Reset the SMC:

M-series Macs: M-series Macs don't have an SMC; a 30-second shutdown is suggested. For persistent issues, consider reinstalling firmware using Apple Configurator 2 (requires another Mac).

Intel Macs:

Apple recommends trying other troubleshooting first, but resetting the SMC is generally safe and can resolve various problems.

• Desktop Macs: Disconnect the power cord for 15 seconds, reconnect, wait 5 seconds, then power on.
• Laptops with T2 chip: Hold the power button for 10 seconds, release, then power on.
• Laptops (no T2 chip), non-removable battery: Hold Control-Option-Shift and the power button for 10 seconds, then release and power on.
• Laptops (no T2 chip), removable battery: Remove the battery, hold the power button for 5 seconds, reinstall the battery, then power on.

There's no Terminal command for resetting the SMC. These procedures aren't guaranteed fixes, but they're worth trying before seeking professional help.

The above is the detailed content of How to reset the NVRAM, PRAM, and SMC on any Mac. For more information, please follow other related articles on the PHP Chinese website!