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iMac restart from sleep - power outage

M

marty1990

macrumors 6502
Original poster
Nov 25, 2011
418
25
England
I have a late 2015 iMac 5K Retina. I was using it last night - and since I'm unsure whether to leave it in sleep mode or turn it off, I alternate between the two depending on how long till I'm next on it.

Last night I placed it in sleep mode.

I got home from work tonight, and the power went off in the kitchen. Once I'd sorted it, I went to my room where my iMac is, the screen was off, and about 5mins later the computer restarted.

Now, I don't know if the power tripped on the circuit my Mac is on. But if it was, would that cause the Mac to restart from sleep mode? And if so, would that cause any damage to my computer? It's turned in fine, but I don't know.

If it doesn't sound like a power outage on the circuit my Mac is on, why would it restart from sleep?

Thanks
 
Check the Preferences settings under Energy Saver -- my guess is that you have "Start up automatically after a power failure" checked.

If so, then that's probably exactly what it was doing.
 
monokakata said:
Check the Preferences settings under Energy Saver -- my guess is that you have "Start up automatically after a power failure" checked.

If so, then that's probably exactly what it was doing.
Click to expand...

I had a quick look online when it happened, and from what I read it's not so great for it to be powered off whilst in sleep mode, and doing so could cause potential issues to the logic board and power supply. I haven't checked yet, will check when am home tonight, but if that setting is enabled, what damage, if any, would there be and how would I know?

Might invest in a UPS.
 
I've never heard that (bad to be powered off during sleep mode) but I think it's widely accepted that having any computer go off, then quickly on, then off, then on . . . is bad. Where I live, it's not rare for the power to go off, then, when it comes back on, to go off again in a minute or so, then back on. This means that any computer set to restart can potentially do a power off before it's finished booting, which is not the best thing to have happen.

A UPS is good, but just setting your Mac to that it won't reboot after a power failure is a less-expensive alternative. I have mine on a UPS, but even so I don't have it set to reboot.
 
Didn't update the thread, the circuit my iMac is on wasn't affected, to confirm, I checked the power settings and "Start up automatically after a power failure" wasn't checked. So I guess it just restarted from sleep for whatever reason.

Still haven't invested in that UPS yet...
 
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