sleep vs. hibernate

I was wondering what the difference is between the two? When should these modes be used? Thanks..

 

People sleep (short term 6-14 hours, and usually less than 24, unless you are pathologic) and bears hibernate (prolonged sleeping typically through the winter season).

I am sorry. I am giddy. I am up all night since I am on call...

Sleep keeps a minimum number of processes going on your computer (HD is off) which drains battery life. I see no advantage to this.

Hibernation saves exactly what processes were running at the time hibernation was initiated but power is off entirely. When you 'wake up' from hibernation, the start up is faster and leaves you right where you left off.

 

I *believe* that sleep will power down almost everything (harddrive, GPU, CPU, display).. But it keeps your state data in RAM. There are no processes running when you are in sleep mode. Since your last state information is kept in RAM, your system can turn on very quickly.. Further, since RAM doesn't use much power (especially if you have DDR2), you can stay in sleep mode for a rather long period of time without draining your battery much.


Hibernate moves the last state data in RAM onto your hard drive. When returning from hibernate, your system will be exactly as it was when you started the hibernate (same as sleep), but your system must load the state information from the hard drive (takes longer). During hibernation, everything is off.. Just like a regular shut down. So your system will not drain battery in hibernation. BUT your last state information is preserved.. And when you start the computer up again, you will be able to resume where you were.

The difference from a cold restart is that both hibernate and sleep can leave windows with unsaved documents open and they will still be there when you return from hibernate/sleep. (Because its saved along with the last-state information).. Although, I wouldn't get into the habit of not saving documents before going into hibernation if I were you.
Depending on the amount of RAM you have and the number of processes running, it MAY take longer to return from hibernate than a cold power on.

 

Hibernation is hardware dependant too. Meaning you can't hibernate with your external USB disk, unplug it and expect Windows to finish cacheing on it. Or even worse - I can change video card with a little switch - GMA900 or Ati x700. If hibernation is done on one config, and then afterwards I change the switch and boot the comp - it will crash and has to delete hibernation data.


Cheers,

 

Now thats interesting.. Although it sounds more like a problem with the design of Windows not expecting a swap of a graphics card while the system is live.. Even though your system changes power cycles.. From the kernel perspective, one instant you're using the old graphics card, and the next you've got a different one. Hot-swapping the graphics card is probably something that is probably not supported in Windows. It really shouldn't be that difficult to catch a graphics card swap and initialize the right drivers. I'd bet Linux wouldn't have as much of a problem.. Probably X server would crash/go down/reset and all your GUI programs will close. But the whole computer itself certainly wouldn't lock up. Xserver will automatically restart and you'd be up and running. Guess that's what happens when you tie the Windows kernel too closely to the CPU/GPU/Chipset.

 

I think sleep it the same as standby...it sends minimal power to only the essential components to keep the laptop running. In hibernation, all data about the computers rinning processes, programs, etc is saved to the hard disk in a file called hiberfile.sys (its usually about 1 GB) and the computer is actually shut down. Standby still conserves a lot of battery power, I once left my computer on overnight on standby (not plugged in) and when I woke up 12 Hrs later, the battery was about 25% full, and I normally only get about 20 mins on my battery.

 

Or maybe it's the drivers are loaded, etc... for one videocard in memory, whereas the others are not. Windows would expect to display using one set, and not have the others.

Kinda like going to sleep with a woman, to find a man in bed next to you when you wake up. Whether that would upset you or not is whether you like Windows or Linux.

 

Szadek, Sidicas,

Yes! I think szadek's approach would describe the issue. Very interesting observation on Linux.

Cheers,

Ivan

 

This is the first I've heard of this. How does DDR2 reduce RAM power in sleep? I thought it just made memory access faster.

 

DDR2 works on lower voltages I think.

 

I remember reading it on Tom's Hardware or PC World.. Anyway, its on Wikipedia too.