PC on Sleep

[jjl]

With W10, power cuts are not a problem - aside from having to hit the front panel power button rather than mashing the keyboard or clicking the mouse to wake them up, they just come back exactly as they were. So they must dump the RAM to HDD or similar - if it's keeping the RAM powered (and refreshed) then I'd expect a similar cold start followed by a nag after the outage.

I have less success with my laptop. If I put it to sleep, the battery does run down reasonably quickly - I suspect that it powers itself up and installs updates (sometimes I look at the event log to see, but normally I'm running about setting up a gig, so don't have time to investigate). Occasionally, even when completely shut down, the battery will still run down. Things improved after a BIOS update which fixed a bug that was introduced by - guess what - a BIOS update! It would probably be fine if I used it at home regularly, but it mostly lives in a flight case awaiting the next gig. I check on it roughly once a fortnight, and allow it to update, etc, at the same time.

When it full "sleep", I'd expect them to use about the same amount of power that they take when plugged in but not switched on. On other words, the main PSU is not running, and just the standby PSU is alive. The standby PSU is normally rated at 10 watts or so, but what is taken from the wall socket will depend on what the motherboard takes. When fully shut down, it only needs to respond to the power switch and wake-on-LAN if enabled (which it usually is by default, but turning that off is well worth doing). When in sleep, it additionally needs to keep the keyboard and mouse powered, but not much else - as mentioned, I don't think it needs to keep the RAM powered and refreshed, else it wouldn't survive power cuts.

Windows "Hibernate" function does store the state of the computer in a file on the hard drive or what have you. When in hibernate, the PC's power consumption will be the same as when it is shutdown.
"Sleep" retains the state in RAM which I believe is placed in a low power, self refresh mode. The CPU is stopped when in sleep and most other peripherals will either be switched off or their clocks stopped. Sleep power consumption will be greater than for shutdown or hibernate.

John

[Mark Hennessy]

I'd agree with that - it matches my understanding from some years back. But today, I'm less clear.

As mentioned, I used "Sleep" most of the time in the XP and W7 days, and if there was a power cut, it would have to start from cold. So this does imply that the RAM remained powered and refreshed.

But with W10, selecting "Sleep" appears to actually put it into hibernation, based on the fact that after a power cut it picks up exactly where it was left, implying that the RAM must be saved to HDD.

I'm talking about several desktop machines here, various ages, etc...

In the case of my laptop, it might well be genuinely sleeping (followed by Hibernate when the battery gets low). In the past I have had half-hearted attempts to figure this out by looking at the logs, but didn't really get anywhere. So I just shut down the laptop, and it's mostly OK. For PCs, I continue to use Sleep - in whatever form it actually is, but "Sleep" is what the menu says. I only reboot for updates

[PerdioPal]

I think Win10 does do sleep also does hibernation as well just in case, quite a good idea.

[Mark Hennessy]

Just to wake up an old thread, quite by chance I stumbled across the answer to this. I was looking for something else entirely, but that's often the way.

In short, Windows 10 has a mode called "hybrid sleep".

This does what I've described above - dumps the RAM to hard disc, like "hibernate", but then enters "sleep", so that it is able to wake when getting input from the keyboard or mouse buttons. Reading around, I've confirmed that RAM remains powered and refreshed, meaning a quick wake-up is assured.

But if power is interrupted, it comes back in hibernate mode rather than sleep, requiring a press of the power switch - and a slightly longer wait - to get it going again... No warnings or nags; you're just exactly back where you were. Lovely :-)

This is the default behaviour for desktop machines; for laptops it's regular sleep (but they have the option of "emergency hibernate" when the battery runs low).

Reading around, it's not clear to me how long "hybrid sleep" has been around. Some sources suggest W7 or even Vista, but I don't have easy access to such machines to check. But certainly, it does appear that "hybrid sleep" is on by default on W10 running on a desktop machine today.

Either way, it's a nice feature for those of us who like to leave our machines in sleep rather than powering them off completely. Power cuts are pretty rare around here, but when they happened, you'd always have the worry about how the various sleeping machines would be when they were next woken up. Today, as I said in my first post here, it's no longer a problem...