The Magic & Mystery Behind SMC and NVRAM / PRAM Resets

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Are you having problems with your MacBook, Mac mini or iMac? Have you tried SMC and PRAM resets?  If not, it’s worth trying. These magic resets can often fix simple software and hardware issues. They certainly can’t hurt and they just might help.

SMC reset? Sounds technical.

SMC, or System Management Controller, is a low-level function that does more or less what it says, it manages system controllers. Straight forward enough for you?

It regulates various hardware functions, mostly those related to power and power consumption.  Problems with a fan spinning too high, LED indicators not working, sleep/wake issues, sensors not reading and a whole host of other problems, can all be solved with an SMC reset. It handles a lot, but here’s a 99% complete list of problems you might run into that could be solved with an SMC reset:

  • MacBook does not respond to the opening and closing of the display.
  • MacBook does not respond to pressing the power button.
  • MacBook is not charging the battery properly.
  • MacBook is not regulating the temperature properly through use of the fans.
  • MacBook does not Sudden Motion Sensor (SMS)
  • MacBook does not adjust screen or keyboard brightness in response to ambient light.
  • Manually adjusting keyboard backlight brightness is non-functional.
  • MacBook’s white LED “status indicator light” does not behave properly.
  • MacBook’s battery status indicator lights are not responsive or otherwise do not behave properly.
  • Problems with an iMac using selecting an external display for video-out.

How does the SMC differ from NVRAM/PRAM?

We’ve talked a little bit about PRAM resets here before. Since then I have found some new info and wanted to clear some things up, so included in this post is a full discussion of NVRAM/PRAM.

NVRAM (Nonvolatile Random Access Memory) and PRAM (Parameter Random Access Memory) perform the same function. NVRAM is the newer version but for all intents and purposes, they do the same thing. NVRAM is basically RAM that doesn’t lose its data when you turn it off. They store information for programs and apps that run when the OS starts. These can be things like volume and display settings, wi-fi and Bluetooth connections, timezone, and startup disk choices. Apple doesn’t release all of the information on what is stored here, but I found an archived version of their website with a fairly full list.  Here is what they included in 2012:

  • Status of AppleTalk
  • Serial Port Configuration and Port definition
  • Alarm clock setting
  • Application font
  • Serial printer location
  • Autokey rate
  • Autokey delay
  • Speaker volume
  • Attention (beep) sound
  • Double-click time
  • Caret blink time (insertion point rate)
  • Mouse scaling (mouse speed)
  • Startup disk
  • Menu blink count
  • Monitor depth
  • 32-bit addressing
  • Virtual memory
  • RAM disk
  • Disk cache

Why Reset?

The real question is “why not?”  There are very few side effects, if any, of trying these resets.  At worst you may lose a few custom boot settings.  There’s no point in doing them if you’re not experiencing any issues, but it is the first thing I do everytime there is an issue.  After doing these resets you know that your machine will be working the way Apple intended it to, assuming you don’t have a much larger issue.  They won’t fix everything, but they just might fix your problem. So, why not try it?

How to perform this magic.

Gaze into my mysterious grimoire of Mac tricks and learn these relatively simple fixes.

The SMC Reset spell:

There are slightly different steps depending on what Mac you are trying to reset.  I’ll start with the easiest one first.

If you are using a desktop Mac, like a Mac Mini or iMac, use the following steps;

  1. Shut down your computer.
  2. Unplug it and wait 15 seconds.
  3. Plug it back in, turn it on and Viola!

See how it easy it is.

On to the laptops.  There are a couple more steps, but it’s still pretty easy.

  1. Shutdown, then unplug your MacBook’s MagSafe power adapter.
  2. If you have a removable battery unplug that, too.
  3. Press Left Shift+Control+Option+Power Button.
  4. Hold these buttons for 10 seconds.
  5. Plug your MacBook back in and start it up.
  6. Enjoy the fruits of your labor.

The NVRAM/PRAM incantation:

This will be the same for all Mac’s.  Once again make sure your Mac is shut down.

The tricky part is going to be you need to turn it back on and hold down the Option+Command+R+P keys.  The easiest way to do this is to hold down Option+Command+R with your left hand, press the power button with your right hand, then quickly bring it to the P key.  On a MacBook you might be able to reach the P key and the power key at the same time with different fingers.  It’s up to you.  Just make sure you have all the buttons held before the Apple loading screen starts.

Now that you have figured out the best way to press all those key, just wait.  You’ll hear your computer make the startup chime, keep holding those keys. After between 10 to 30 seconds, your Mac will restart.  You can let go now and let it start normally.  I like to run through the NVRAM/PRAM reset three times before letting it start normally.  Some people do more, some people do less.

What now?

That’s all there is to it.  You have successfully learned the mysterious secret of the SMC and NVRAM/PRAM reset. I recommend doing both if you are having an OS or hardware related problem, after all it really can’t hurt.  Besides, if you’re going to start casting magic spells on your computer you might as well use your full strength.  You’d be amazed at the number of quirks I have seen relieved by this simple method.

If you’re still experiencing problems, then you may have a larger issue and might need a more experienced repair technician to take a look.

About The Author

Brite Cheney

I am an English major at CSU, Chico with a lifelong interest in computers and technology, and joy for writing about all things tech.

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Hi man, good article. I ve been experiencing problems with keyboard and mouse. Suddenly the left button on mouse start behavig like right button. And command and option buttons start misbehaving too. I ve been experiencing this since the upgrade from yosemite to sierra. I thought this was going to stop when I upgraded from sierra to high sierra, but no. The recovery partition is gone, just for the récord. I read on internet that other users had experienced this same error (recovery partition gone) when they upgraded to high sierra. I have been trying to do the pram reset… Read more »

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