Mac是一台可靠的机器，但在极少数情况下，它可能会无缘无故地开始表现怪异或崩溃。
您可能会注意到一些奇怪的行为，例如键盘没有正常响应(keyboard not responding normally)、指示灯和指示灯无法正常工作或操作系统运行速度比平时慢。其他奇怪的症状可能包括Mac 拒绝正常充电(Mac refusing to charge properly)、意外进入睡眠状态或根本无法启动。
您可以通过基本的重新启动和其他故障排除技巧来解决其中一些问题。但是，如果它们仍然存在，您需要在Mac上重置(Mac)PRAM和SMC。
什么是 PRAM 和 SMC？(What Is PRAM & SMC?)
PRAM（参数 RAM(Parameter RAM)）存储有关Mac控制设置的重要信息。这些设置包括显示、时区、扬声器音量等。PRAM由内置电池供电，因此即使您关闭Mac ，您的设置也不会丢失。
在现代Mac(Macs)中，PRAM被称为NVRAM（非易失性RAM），其用途与PRAM相同。PRAM和NVRAM之间的主要区别在于，即使两者都可能损坏，但NVRAM并不常见。
SMC（系统管理控制器(System Management Controller)）集成在基于 Intel 的Mac的(Mac)主板中，用于管理(motherboard )Mac的核心任务。电源、灯光、风扇和系统性能等任务(Tasks)属于SMC。
当您的Mac开始出现异常时，您可以重置PRAM和SMC以让您的Mac恢复工作状态。
什么时候应该在 Mac 上重置 PRAM？(When Should You Reset PRAM On Your Mac?)
正如我们已经看到的，Mac中的PRAM/NVRAM管理基本控制设置，例如扬声器音量、鼠标速度、启动字体、启动磁盘、虚拟内存、磁盘缓存、端口配置和许多其他操作方面。您可以调整这些设置，但也可以重置PRAM/NVRAM以修复多种行为，包括：
- 日期和时间错误，或时区错误。
- 音量不粘。
- Mac经常从错误的驱动器启动。
- 启动时出现问号。
- 奇怪的鼠标滚动速度(mouse scrolling speed)。
- 显示分辨率不变。
何时应该在 Mac 上重置 SMC？(When Should You Reset SMC On Your Mac?)
(SMC)另一方面，SMC管理Mac的核心硬件功能，因此如果您遇到与此类核心任务相关的一个或多个问题，则需要重置SMC。
此类问题包括但不限于：
- Mac意外休眠或关闭。
- 键盘(Keyboard)背光、电池指示灯、显示屏背光和状态指示灯行为不正确。
- 电池似乎无法正常充电(Battery doesn’t appear to be charging properly)。
- 显示(Display)亮度无法正常工作。
- (Mac)即使CPU(CPU)使用率很低， Mac的运行速度也异常缓慢。
- 球迷们跑得又快又响(Fans running loudly and fast)。
- 蓝牙(Bluetooth)和USB端口不工作。
- 无法识别外部设备。
- 电源键不好用。
- 当您打开或关闭盖子时， Mac(Mac)无法正确响应。
- 未从睡眠中醒来或未进入睡眠(not entering sleep)。
- 电源(Power)指示灯不显示或显示不正确。
- 目标显示模式(Display Mode)正常工作。
- Bouncing Dock图标在不打开相关应用程序的情况下不断弹跳。
如何在 Mac 上重置 PRAM(How To Reset PRAM On Your Mac)
(Resetting your Mac)在对诸如重新启动和其他加速计算机缓慢故障的技巧等选项进行故障排除时，(speed up a slow computer)重置 Mac应该是最后的手段。
在您重置Mac上的PRAM和SMC之前，请先备份所有重要资料。您可以将它们备份到外部驱动器或USB密钥。此外，您需要断开所有扬声器、加密狗、驱动器、外接显示器和键盘的连接，以免干扰重置过程。
重置Mac上的PRAM/NVRAM将硬盘驱动器设置为启动磁盘并恢复默认硬件设置(restores the default hardware settings)。
- 要重置PRAM/NVRAM，请关闭Mac，打开电源并同时按住Option、Command、P和R键。大约 20 秒后松开按键，您的Mac将重新启动。
注意(Note)：如果您的Mac播放启动声音，请在第二次启动声音后松开四个键。如果您的Mac 带有 Apple T2 安全芯片，请在(Mac with the Apple T2 Security Chip)Apple标志出现然后再次消失后松开按键。
- 如果您的Mac使用固件密码（意味着没有密码的其他用户只能从指定的启动盘启动），则您必须在重置NVRAM之前关闭固件密码。
- 启动完成后，打开系统偏好设置(System Preferences)并调整任何已重置的设置，例如显示分辨率、音量、时区或启动磁盘选择等。要打开系统(System) 偏好设置(Preferences)，请单击Apple menu > System Preferences或单击Dock中的(Dock)系统(System) 偏好设置(Preferences)图标。
注意(Note)：对于台式机Mac(Macs)，您可能需要更换电池，以防每次关闭并拔下计算机时都会重置时区或音量等设置。
如何在 Mac 上重置 SMC(How To Reset SMC On Your Mac)
在Mac上重置SMC会恢复与您无法在“(SMC)系统偏好设置”(System Preferences)中修改的低级设置相关的默认设置。SMC重置取决于您使用的Mac ，(Mac)它是否具有可拆卸或内置电池，以及是否从墙上耗尽电源。
- 要在Mac上重置SMC，您需要关闭Mac。如果计算机无法关闭，请按住电源按钮约 10 秒钟或直到Mac关机。
- 如果您的Mac 配备(Mac)Apple T2 安全芯片(Apple T2 Security Chip)，请关闭(shut down)电脑，按住电源按钮 10 秒后松开。
- 按电源按钮(power button)打开 Mac。
- 如果Mac仍然没有应有的响应，请将其关闭，然后同时按住Control、Option和Shift键约 7 秒钟。同时按住电源(Power)按钮并等待Mac关机。
- 按住Control、Option、Shift和Power按钮 7 秒钟，然后松开它们。
- 按电源(Power)按钮打开Mac并检查它是否再次正常工作。
对于带有Apple T2 安全芯片的台式机(Apple T2 Security Chip)Mac(Macs)，请关闭计算机并拔下电源线。等待(Wait)10-15秒，插回电源线，5秒后按电源键开机。
注意(Note)：重置SMC不会影响PRAM/NVRAM的内容。
- 要在没有Apple T2 安全芯片的(Apple T2 Security Chip)Mac(Macs)上重置SMC ，请关闭Mac，然后按住Shift、Control和Option键。
- 在按住Shift、Control和Option键的同时，按住电源(Power)按钮。按住所有四个键 10 秒钟。
- 10 秒后松开四个键，然后按下电源(Power )按钮打开 Mac。
如果您的Mac笔记本电脑带有可拆卸电池，请关闭(shut down)Mac 并取出(remove)电池。按住电源(Power)按钮 5 秒钟，重新安装(reinstall)电池，然后按电源(Power)按钮打开Mac。
对于没有Apple T2 安全芯片(Apple T2 Security Chip)的台式Mac电脑，请关闭Mac，拔下电源线并等待 15 秒钟，然后再重新插入电源线。再等待(Wait)5 秒钟，然后按下电源(Power)按钮打开电脑。
如果PRAM/NVRAM或SMC重置不起作用，请尝试使用Apple 诊断程序(Diagnostics)或Apple 硬件测试(Apple Hardware Test)（适用于 2013 年 6 月(June 2013)之前推出的Mac(Macs)）。这些测试包含一套诊断程序，用于测试您的 Mac(suite of diagnostics that test your Mac)是否存在硬件问题、提出解决方案并帮助您联系Apple 支持(Apple Support)以获得进一步帮助。
让您的 Mac 再次工作(Get Your Mac Working Again)
如果您的Mac出现异常行为，重置PRAM或SMC（或两者）将使其恢复正常运行。使用这些步骤后，您的Mac是否正常运行？(Mac)在评论中与我们分享。
How To Reset PRAM & SMC On Your Mac
A Mac is a reliable machine, but on rare occasions, it might stаrt acting weird or сrashing for nо apparent reason.
You may notice some strange behaviors such as the keyboard not responding normally, lights and indicators not working correctly, or the operating system acting slower than usual. Other strange symptoms can include the Mac refusing to charge properly, entering sleep unexpectedly, or not booting at all.
You can solve some of these problems through a basic reboot and other troubleshooting tips. However, if they persist, you’ll need to reset the PRAM and SMC on your Mac.
What Is PRAM & SMC?
PRAM (Parameter RAM) stores vital information about your Mac’s control settings. These settings include a display, time zone, speaker volume, and more. PRAM is powered by an internal battery so that your settings aren’t lost even when you turn off your Mac.
In modern Macs, PRAM is known as NVRAM (non-volatile RAM), which serves the same purpose as PRAM. The main difference between PRAM and NVRAM is that even though both can get corrupted, it’s not as common with NVRAM.
SMC (System Management Controller) is incorporated into the motherboard of an Intel-based Mac and manages core tasks of your Mac. Tasks like power, lights, fans, and system performance fall under the SMC.
When your Mac starts acting strange, you can reset PRAM and SMC to get your Mac back to a working state.
When Should You Reset PRAM On Your Mac?
As we’ve already seen, the PRAM/NVRAM in your Mac manages basic control settings such as speaker volumes, mouse speed, startup fonts, startup disk, virtual memory, disk cache, port configuration, and many other operating facets. You can adjust these settings but you can also reset the PRAM/NVRAM to fix several behaviors including:
- Wrong date and time, or wrong time zone.
- Sound volume not sticking.
- Mac constantly boots from the wrong drive.
- Question mark appearing at startup.
- Weird mouse scrolling speed.
- Display resolution not changing.
When Should You Reset SMC On Your Mac?
SMC, on the other hand, manages the core hardware functions of your Mac, so if you experience one or more issues related to such core tasks, you’ll need to reset SMC.
Such issues include but aren’t limited to:
- Mac sleeps or shuts down unexpectedly.
- Keyboard backlight, battery indicator light, display backlight, and status indicator lights behave incorrectly.
- Battery doesn’t appear to be charging properly.
- Display brightness not working right.
- Mac runs unusually slowly even with little CPU usage.
- Fans running loudly and fast.
- Bluetooth and USB ports not working.
- External devices are not recognized.
- Power button doesn’t work well.
- Mac doesn’t respond properly when you open or close the lid.
- Not waking from or not entering sleep.
- Power indicator not displaying or displaying incorrectly.
- Target Display Mode working correctly.
- Bouncing Dock icons keep bouncing without opening the related apps.
How To Reset PRAM On Your Mac
Resetting your Mac should be a last resort when troubleshooting options such as rebooting and other tricks to speed up a slow computer failure.
Before you can reset the PRAM and SMC on your Mac, have a recent backup of all your critical stuff. You can back them up to an external drive or a USB key. Plus, you need to disconnect all speakers, dongles, drives, external displays, and keyboards so that nothing will interfere with the resetting process.
Resetting the PRAM/NVRAM on your Mac set the hard drive as the startup disk and restores the default hardware settings.
- To reset PRAM/NVRAM, shut down your Mac, power it on and press and hold the Option, Command, P, and R keys together at the same time. Release the keys after 20 or so seconds and your Mac will appear to restart.
Note: If your Mac plays a startup sound, release the four keys after the second startup sound. If you have a Mac with the Apple T2 Security Chip, release the keys after the Apple logo appears and then disappears a second time.
- If your Mac uses a firmware password (meaning that other users without the password can only start up from the designated startup disk), you’ll have to turn off the firmware password before resetting NVRAM.
- Once the startup is completed, open System Preferences and adjust any settings that were reset like display resolution, sound volume, time zone, or startup disk selection among others. To open System Preferences, click the Apple menu > System Preferences or click the System Preferences icon in the Dock.
Note: For desktop Macs, you may need to replace the battery in case settings like time zone or sound volume are reset each time you shut down and unplug your computer.
How To Reset SMC On Your Mac
Resetting the SMC on your Mac restores default settings related to low-level settings that you can’t modify in the System Preferences. An SMC reset depends on the Mac you’re using, whether it has a removable or built-in battery, and if it runs off power from the wall.
- To reset SMC on your Mac, you’ll need to shut down your Mac. If the computer won’t shut down, press and hold down the power button for about 10 seconds or until the Mac powers off.
- If your Mac has the Apple T2 Security Chip, shut down the computer, press and hold the power button and release it after 10 seconds.
- Press the power button to turn on your Mac.
- If the Mac still doesn’t respond as it should, shut it down and then press and hold Control, Option and Shift keys at the same time for about 7 seconds. Press and hold down the Power button as well and wait for the Mac to go off.
- Hold down the Control, Option, Shift, and Power button down for another 7 seconds and then release them.
- Press the Power button to turn on your Mac and check if it works normally again.
For desktop Macs with the Apple T2 Security Chip, shut down the computer and unplug the power cable. Wait for 10-15 seconds, plug back the power cable, and then press the power button after 5 seconds to turn on the computer.
Note: Resetting SMC doesn’t affect the contents of PRAM/NVRAM.
- To reset SMC on Macs that don’t have the Apple T2 Security Chip, shut down the Mac, and press and hold down the Shift, Control, and Option keys.
- While still holding the Shift, Control, and Option keys, press and hold down the Power button. Hold all four keys for 10 seconds.
- Release the four keys after 10 seconds and press the Power button to turn on the Mac.
If you have a Mac notebook with a removable battery, shut down the Mac and remove the battery. Press and hold the Power button for 5 seconds, reinstall the battery, and then press the Power button to turn on the Mac.
For desktop Mac computers without the Apple T2 Security Chip, shut down the Mac, unplug the power cable and wait 15 seconds before plugging the cable back in. Wait another 5 seconds and then press the Power button to turn on the computer.
If a PRAM/NVRAM or SMC reset doesn’t help, try using the Apple Diagnostics or Apple Hardware Test (for Macs introduced before June 2013). These tests contain a suite of diagnostics that test your Mac for hardware issues, suggest solutions, and help you contact Apple Support for further assistance.
Get Your Mac Working Again
If your Mac has been misbehaving, resetting the PRAM or SMC (or both) will get it back to operating as you expect it to. Is your Mac running normally after using these steps? Share with us in a comment.
