Originally published at: http://www.howtogeek.com/165110/do-i-really-have-to-unplug-my-cable-modem-for-at-least-10-seconds/
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So that's why my laptop's charging light stays on for about a minute when it's shut down and the charger is removed.
Yup! It's also why techs tell you to shut down for a minimum of 30 seconds for a PC, when you're trying to resolve problems. I can't tell you how many times I've had users try to do a "Reboot", when I said "Shutdown", for this reason. Once I got them to do the correct action, problems were usually resolved.
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.
But surely the router wipes the RAM when it is initialised so it does not need the RAM to be wiped, as its "cleaned" when it is initialised.
One would think that the programmer would always clear the RAM. But if your assumption is the device is starting from a powered off state, why bother to clear it? I've found from personal experience that waiting that short amount of time before plugging something back in clears up a lot of random problems vs unplugging and immediately plugging it back in. But your mileage may vary.
I generally unplug the modem and router, wait 10 seconds, plug modem back in, wait 30 seconds for it to initialize, then plug in the router; works pretty well, and gives all the equipment time to get set up properly.
I have always wondered if it were possible to wipe the RAM without having to shut down the computer. When there are computer problems, it'd be nice to be able to wipe the memory clean, on the fly. Does anyone know if this is possible?
Sure there is! Open your case (with the PC on) and remove the RAM. You'll probably get an electric shock and die, though.
Oh yeah, and don't forget to ground yourself first otherwise you might short out or otherwise kill your MoBo/Ram.
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That's what it's SUPPOSED to do, yes. But router RAM and PC RAM both occasionally do "hold on" to random data while powered up, even during a reboot, if the power is never severed.
There are apps out there that do "Memory Optimization" or Memory Reclamation that kind of do this. But it doesn't do all of the RAM. In a computer, everything happens in RAM - even the operating system. So if you were truly clear out all RAM, even for a millisecond, your computer would crash - hard.
So, at best, you can hope for reclaiming the RAM allotment from applications with memory leaks - but any more than that means something has to crash.
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Yes, indeed, the system would crash if the all RAM were wiped clean. But hasn't someone designed an application that would enable one to selectively choose which elements of RAM to wipe, thus keeping the computer operating? Tricky, no doubt, but nonetheless quite a desirable little app.
When working with my router, it always says to do a hard (30/30/30) reset. This is where you hold in the reset button, with a paperclip, for 30 seconds, then pull the power cable for another 30 seconds, still holding in the reset button, then re-plug the power cable, still holding the reset button for another 30 seconds. That completely wipes everything from the router and resets to factory default. After that I have to re-install the DD-WRT firmware I had put on it and set my whole house up again, so I only do this as a last resort!
It would be really, really, really easier to just:
Shut the PC down.
Remove power cable (if it's a laptop, remove the battery too).
Wait a few seconds (memory clears).
Start the PC.
Takes about two minutes, and has the cool side effect of installing any pending Windows updates.
The flaw in your logic is that if you don't power down long enough, the RAM doesn't get fully wiped and the device never initializes, so it never gets a chance to wipe the RAM. Technically, the statement is wrong - a program never assumes RAM is "wiped". It always writes the data values it expects to find later in RAM, whether it's numbers or all zeros.
But that's not the real reason for waiting to re-power a device. In actuality, there is a small reset circuit in microprocessor devices that detects when the power supply increases and reaches the correct voltage(s), then sends a pulse to reset the microprocessor.
If you don't power down long enough, the voltage stays high enough that the reset circuit never detects an increasing voltage and never sends that pulse to reset the microprocessor. At that point, RAM could have become corrupted from the power outage and/or the microprocessor just starts running from a random place in memory because it was never reset. That's enough to hang the device.
There is no standard defining how fast a power supply should drop it's voltages to zero, but us technical folks know from experience that almost all devices will have fully powered down after 30 seconds. That's really a bit of overkill (longer than necessary) for many devices, but there is no better way to be reasonably sure that any one given device will reinitialize properly.
That's the real reason why powering down and waiting 30 seconds before powering back up has became a rule of thumb. That half minute can seem like an eternity, but it's much faster than waiting 10 or 15 seconds, powering up, figuring out that the device has hung, then powering back down and waiting the full 30 seconds after all.