Do I Really Have to Unplug My Cable Modem for at Least 10 Seconds?

You’ve heard it time and time again from tech support staff: “Alright, let’s unplug your (router/modem/time machine) for X number of seconds, and then plug it back in…” but why exactly are you doing it and does it matter if you do it for 10, 20, or 30 seconds (if it matters at all)?

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

The Question

SuperUser reader Swish wants to know why exactly he’s always being instructed to unplug things:

When calling support the other day he told me to reset my DSL modem by pulling out the power, leave it out for 10 seconds, and then plug it back in. This is something I have heard many times with different kinds of equipment. I have also heard it in relation to computers. That when you turn it off, you should wait at least 10 seconds before you turn it on again.

1. Why not just plug it in again right away?

2. Why 10 seconds, instead of, say… 3 or 30?

3. Should you really, always do this; just with certain types of equipment; just in certain circumstances; or is it just a “myth” thing that people have said so often that they believe it to be fact?

These are all valid questions: why do we do it and does it even help?

The Answer

SuperUser contributor Phoshi offers a great, concise reason why it’s a valid procedure:

A lot of modern technology contains capacitors! These are like energy buckets, little batteries that fill up when you put a current through them, and discharge otherwise. 10 seconds is the time it takes most capacitors to discharge enough for the electronics they’re powering to stop working. That’s why when you turn your PC off at the wall, things like an LED on your motherboard take a few seconds to disappear. You probably could wait a different time, but 10 seconds is the shortest time you can be sure everything’s discharged.

Why fully powering down the device matters hinges on how data is temporarily stored in it. A typical modem or router has two types of memory: Non-volatile Memory (NVRAM) and regular old Random Access Memory (RAM) like the kind in your computer. The router boots off the code stored in the NVRAM and then uses the RAM just like your computer would to write temporary variables, execute code, etc. By fully powering down the device and letting the electrical charges dissipate, the RAM is wiped and, upon rebooting the device, the micro operating system in the device has clear RAM to use.

Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.