Instructions: NVRAM, PRAM and SMC reset on Mac - reset to solve problems

NVRAM reset, PRAM reset, SMC reset, instructions, Apple Mac, MacBook

Here you will find instructions for resetting or resetting NVRAM, PRAM and SMC on the Apple Mac or MacBook. Many problems that arise when using the Apple Mac can be solved by resetting these three things. Often there are also reader questions here on the blog, the answer to which lies in resetting NVRAM, PRAM and / or SMC. In addition to the instructions for Do It Yourself, I would also like to briefly explain the individual terms.

Update June 22, 2020: Instructions for the SMC reset on Mac and MacBook with T2 Security Chip (End of update)

Resetting RAM and cache memory as well as the control chip: Instructions for the NVRAM, PRAM and SMC reset can be found here

Resetting RAM and cache memory as well as the control chip: Instructions for the NVRAM, PRAM and SMC reset can be found here

A brief explanation of terms: What are NVRAM, PRAM and SMC?

Before we get to the reset of NVRAM, PRAM and SMC, let's first clarify the terms. Not every user knows what to do with NVRAM, PRAM and SMC and may therefore shy away from resetting them accordingly. So here is a brief explanation of the three abbreviations for you:

NVRAM "Non-volatile random access memory“, A non-volatile memory that comes close to RAM, but remains in place even without an external power supply. Unsegmented, hardly limited and non-overwriting memory - hence sometimes a "garbage cache".
PRAM "Random Access Memory parameter“, A memory not dissimilar to NVRAM, but which mainly contains data from the operating system. Among other things, OS X or macOS stores data such as volume, font formation, alarm settings, monitor data, double-click intervals, the hard drive cache, etc. in the PRAM.
SMC "System Management Controller“, A chip on the motherboard of the Mac or MacBook that controls voltage-dependent functions (also and above all of the hardware). Affected here are the fan, USB ports and USB devices, the Bluetooth module, etc. The SMC reset thus solves minor hardware problems and the associated system failures / overloads.

Instructions for NVRAM and PRAM reset: Reset the Mac RAM

Only older Mac models have a PRAM, most newer devices only use NVRAM. Therefore there is only one guide for resetting NVRAM and PRAM. And this is how it works:

  • Turn off your Mac or MacBook (if not already off)
  • Turn on your Mac or MacBook
  • Hold Command + Option (Alt) + P + R (⌘ + ⌥ + P + R) during system startup
  • When the system starts to sound for the second time, release the buttons
  • Then checks information such as the boot hard disk / boot partition, display and time or dates and other system settings; if necessary adjust them again to your preferences

There are problems? Trouble shooting during NVRAM reset

It can happen that when resetting the non-volatile random access memory or the parameter random access memory nothing happens and you only get a gray screen. Here it can help to unplug all USB or Thunderbolt devices. Take the peripherals off the Mac (except of course the keyboard, if it's wired) and switch off the Mac (if it doesn't catch itself and remain in its gray shock). Then repeat the above procedure.

Before we get to the System Management Controller Reset ...

Apple thinks that if you have system problems, i.e. if the hardware is crazy, you shouldn't reset the SMC first. Rather, one should end problematic tasks, restart the computer and so on. If that doesn't help or if the problems keep recurring after the restart, then you should consider the following steps. Apple shows no negative consequences of the reset. Therefore you can use it for trouble shooting.

Instructions for the SMC reset: Reset the system management controller chip

There are different measures to reset the SMC for stationary Apple computers and for various MacBook models. Here I would like to show you the three different approaches. In preparation, the Mac or MacBook must first be shut down (force shutdown if necessary).

There are these differences when resetting:

  • Desktop Mac: Turn off the Mac, disconnect the power cord from the power supply for 15 seconds, then wait another 5 seconds and turn the Mac on again
  • MacBook with removable battery: Remove the MagSafe power supply unit, remove the battery, press the On / Off button for 5 seconds, insert the battery, switch on
  • MacBook with a fixed battery: Remove the MagSafe or USB-C power supply, Shift + Ctrl + Option (Alt) (everything on the left side of the built-in keyboard) and press the On / Off button for 10 seconds, release, plug in the power supply, switch on

Indication that the SMC may need to be reset

The subheading and the following list are to be understood as quotations. The source is this Apple support page. Here are the cases listed there in which you can consider an SMC reset to solve the problem:

  • The computer fans run at high speed even though the computer is not being used heavily and is well ventilated.
  • The keyboard backlight is behaving incorrectly.
  • The status light behaves incorrectly.
  • The battery status indicator, if present, behaves incorrectly (on Mac notebooks without a removable battery).
  • The display backlight does not respond properly to changes in ambient lighting.
  • The computer does not respond when the power button is pressed.
  • The Mac notebook does not behave properly when it is opened or closed.
  • The computer goes to sleep or turns off unexpectedly.
  • The battery is not charging properly.
  • The MagSafe power supply LED does not indicate activity properly.
  • The computer is unusually slow even though it is not using an unusually high CPU load.
  • Program icons "jump" in the Dock for an excessive amount of time when the associated programs are opened.
  • Applications do not work properly or stop responding after opening.
  • A computer that supports the screen synchronization mode does not switch to the target screen or back suddenly as expected or suddenly.
  • Lights around I / O ports on a Mac Pro (Late 2013) don't turn on when you move the computer.

Any questions?

Were these instructions helpful or missing a detail? Is something unclear or could I help you? Feel free to leave a comment about the reset of NVRAM, PRAM and SMC;)

-
Do you like my blog? Then I would be happy to receive a short review on Google. Easy leave something here for a moment - that would be great, thank you!

15 comments

  1. Sascha says:

    Where does an iMAc write, what kind of keyboard does it start with? At
    Thanks to my iMac, I often have to change the keyboard layout to enter the hard disk password, but not always because it is in the wrong language.

    • Sir Apfelot says:

      Hey Sascha! I don't know exactly in which RAM it is saved, but with me this has now occurred in exceptional cases with the wrong keyboard layout. I think times during a recovery or during an action with the hard disk encryption. As far as I know, resetting NVRAM, PRAM or SMC will not affect this. I recently did these resets on an iMac and was still able to log in with a password (which also contained umlauts). Maybe a reader has more information ... but unfortunately I don't know exactly when this will occur with the US keyboard layout. VG! Jens

  2. Sandro says:

    Hallo,
    can i do a PRAM and an SMC reset on an iMac at the same time, or does it cause complications?
    (In other words: switch off and disconnect from the power supply; wait 15 seconds; plug in; wait 5 seconds; press Alt CMD PR and switch on)
    I have to do this more often with my somewhat older and heavily used iMac and now wonder whether this can have negative consequences.
    Many thanks for the answer

    • Sir Apfelot says:

      Hi Sandro! That doesn't actually have any negative consequences. It's just a deletion of a cache. It may take a little longer for the Mac to boot for the first time, but nothing more should happen. What problems are you having with your iMac that you need to perform these resets? LG! Jens

    • Markus says:

      Hello, I also have this phenomenon every now and then. which OS do you have with the problem? I use an external Logitech keyboard (macOS Mojawe) and it is not recognized during a reboot if I do not want to enter my password when logging in. The computer recognizes other keyboards from Apple and Kannex. after booting the keyboard is back ... I have the whole thing on a Macbook Pro and a Macbook. Anyone have an idea? I did Nvram and SMC.

      • Sir Apfelot says:

        Hi Markus! With some keyboards you have to type a bit when logging in before they pair. But what surprises me: Logitech normally supports Macs quite reliably. Unfortunately, I don't know why the keyboard doesn't work ... I also have no idea what to do with it. Has the problem been since Mojave or before?

        • Markus says:

          Hello, the problem has only appeared since Mojawe. And as I said, both on the Macbook Pro and on my little Macbook. Specifically, it's about the Logitech Craft and the MX Ergo trackball. I also do Apple support myself, but at the moment I don't know what to do next.

  3. Klaus says:

    Hello, my iMac (older model) takes forever to start. After entering the PIN, the beach ball runs continuously. Would a PRAM reset be worthwhile? I have Yosemite on it. thanks

    • Sir Apfelot says:

      Hello Klaus! You can't go wrong with the reset. With a slow system start you could also check whether the start volume is set correctly and, if necessary, check where it "hangs" by restarting in Verbose mode (hold down the cmd + V key during restart). Most of the time it gives an error there. You can then view these logs in the console (Utilities> Console) and see why it is hanging. LG! Jens

  4. Joachim says:

    I have the problem that my iMac (Late2017) loses the bluetooth connection after booting, but not always, and logging in for several minutes, first mouse, then keyboard, even after waking up. But not always. I also connected a cable mouse and when I go to Bluetooth with this in the head bar, the rotating ball comes

  5. Rainer says:

    Hello. Apparently I'm doing something wrong with the safe boot. Immediately after the on / off switch, I press Shift and still don't get a bar but the normal login screen. It worked once, not since then. Urgently need to remove incompatible software that is preventing the system from starting. Is there still another possibility? Regards, R

    • Sir Apfelot says:

      Hello Rainer! We're talking about the same key, aren't we? The Shift key that is used to make capital letters. : D An alternative would be to boot with CMD + R and then delete the corresponding data on the hard disk via the terminal. You won't get a real finder there. Or the last - somewhat cumbersome - solution: boot with CMD + R, then install a fresh system on an external hard drive, boot from there and then delete the incompatible program from the internal hard drive. I hope you can somehow manage it. LG!

  6. Reinhard Brakel says:

    Hello my dears. My MacBook Pro at the end of 2008 starts up as usual, but the startup process aborts and turns off again. What can I do?

    • Jens Kleinholz says:

      Hello Reinhard! Does he do that when he's on the cable? Have you ever tried booting with the SHIFT key pressed (Safe Mode)? Or boot in recovery mode (with pressed CMD + R key)? I would try to restore an external hard drive with a fresh macOS and boot from it. The system may have a problem on the internal disk. If you want more answers from other readers, I would give you that Sir Apfelot Forum recommend. There are already some experts out there who have more knowledge than I do. : D

Leave a Comment

Your e-mail address will not be published. Required fields are marked with * .