eli5: Does it matter to a computer how long it’s powered off for? Is one micro-second as good as 5 minutes? If not, why and how long is optimal for it to be powered off for?

Question

That is the question. I almost never turn off the computer, but sometimes flick it off for just a second or two. Is this bad for it? Does it need rest? Thanks!

In: 1752

Answer 1

Most computers will need around half a second to turn off completely before restarting, to make sure everything is in a clean state. This is mostly due to capacitors (battery-like devices inside the computer that store a bit of power) needing to discharge.

If the system is restarted too fast, the system won’t be in a clean state and won’t likely be able to start up properly. For computer systems that are restarted using the soft-restart feature (e.g. clicking “restart”), this turns off all the major components within the system that need to be reset before turning them back on again.

Most modern computer systems will delay a restart if a problem is detected, this is why often if you need to forcefully shut down your computer using the power button, it won’t turn back on straight away if you immediately press the button again after the system turns off. This is done for the same reason: making sure everything is in a clean state.

What most people don’t realise is that literally everything, even the most well-engineered devices, are held together using proverbial sticky tape. In a typical device you have components from at least a dozen different manufacturers and all of them will have different specs: what always works to ensure everything is in a good state before turning the system back on is introducing a delay.

Source: software engineer for embedded systems, and I’ve come across Nvidia’s specs for their Jetson modules on this.

For example, for the Jetson AGX Orin (like a Raspberry Pi but a *lot* beefier), the main power rail needs to go below 100mV before the system is considered to be fully reset. The implementation guide (which tells you how to make a circuit board you can install the module on) gives 20ms as the time taken from when full power is removed and when the main power rail goes below 100mV, but with a 10% margin of error.