when my i5 MBP battery runs out it hibernates!

[millerb7]

Hibernation uses no power. Hibernation completely shuts off the computer. That's why it needs the contents of RAM written to the HD.


This is correct. But on Macs, the contents of RAM are simultaneously written to the HD as you said later on. This is what OS X calls "Safe sleep". Just in case your computer runs out of power while sleeping, it will still resume its state fine from disk.


Also kind of correct. When a Mac is sleeping and runs out of power, it just shuts itself off. The RAM image is already written to the HD at this point due to Safe Sleep.

While in hibernation, there is still power in the battery, is what I was meaning. That is the entire reason when you are calibrating you are to let the machine sit for roughly 5 hours to COMPLETELY kill it, or to hold the power button down after it is in hibernate. I guess I worded it poorly... I wasn't meaning that the hibernation was actually still using power, just that the batteries still have juice in them.

On macs the content of the ram is written to the HDD simultaneously when it's in hibernatemode 3. If it's in lets say, 0, like mine, that is not the case.

I personally see NO reason to use hibernatemode. Just seems silly. When you let your machine idle, or shut your lid, SAVE YOUR WORK!!! There is also no need to drain your battery that low that often. To me it's just wasted space on the HDD.

 

[Menge]

On macs the content of the ram is written to the HDD simultaneously when it's in hibernatemode 3. If it's in lets say, 0, like mine, that is not the case.

I said "on Macs" in a general way because to change the hibermatemode flag you need to open the Terminal and do some "wizardry" there. It's not the default setting nor does it seems too supported, since Apple doesn't supply the proper UI to choose it.

Anyway, it's pretty amazing how much confusion there is around Sleep, Safe Sleep and Hibernation and how they work and when they act. Let's hope mine and your posts can help these guys understand this better

 

[prism]

Millerb7, sorry but now I am really confused. If hibernation uses no power why would letting it sit for 5 hours drain the batteries? Something needs to drain it in the first place, what would it be?

While in hibernation, there is still power in the battery, is what I was meaning. That is the entire reason when you are calibrating you are to let the machine sit for roughly 5 hours to COMPLETELY kill it, or to hold the power button down after it is in hibernate. I guess I worded it poorly... I wasn't meaning that the hibernation was actually still using power, just that the batteries still have juice in them.

On macs the content of the ram is written to the HDD simultaneously when it's in hibernatemode 3. If it's in lets say, 0, like mine, that is not the case.

I personally see NO reason to use hibernatemode. Just seems silly. When you let your machine idle, or shut your lid, SAVE YOUR WORK!!! There is also no need to drain your battery that low that often. To me it's just wasted space on the HDD.

 

[millerb7]

Millerb7, sorry but now I am really confused. If hibernation uses no power why would letting it sit for 5 hours drain the batteries? Something needs to drain it in the first place, what would it be?

1. See my signature

2. To calibrate a portable computer battery:

1.

Plug in the MagSafe Power Adapter and fully charge the battery.

When the battery is fully charged, the light on the MagSafe Power Adapter connector changes to green and the Battery icon in the menu bar indicates that the battery is charged.
2.

Allow the battery to rest in the fully charged state for two hours or longer.

You can use your computer during this time as long as the power adapter is plugged in.
3.

With the computer still on, disconnect the power adapter and continue to use your computer.
4.

When you see the low battery warning, save your work and close all applications. Keep your computer turned on until it goes to sleep.
5.

After your computer goes to sleep, turn it off or allow it to sleep for five hours or longer.
6.

Connect the power adapter and leave it connected until the battery is fully charged.

You can use your computer during this time.

This is directly from apple. I HAVE to assume the reason you need to turn off the computer, or let it sit for 5 hours, is to finish FULLY draining the battery. I know when I do it, and it goes to hibernate, if you then hold down the power button you can hear the computer FULLY shutdown....

I'm not a master at the exact battery specifics, but to me, if you need to shut it of (or just the fact that you CAN shut it off) or let it sit for 5 hours, means there is still some charge left in the battery, it's just not enough to power the computer or enough to keep the image no the RAM... which is why your image is written to your HDD.

 

[tjb1]

Personally I would just set hibernatemode to 0 and erase the sleep file and be done with it.

sudo pmset -a hibernatemode 0

sudo rm /var/vm/sleepimage

Im not sure if the rm needs sudo...

If you have 8gb of ram, this will save you 8gb of hdd space, 4gb of ram will save you 4gb of hdd space.

 

[prism]

So you are saying in steps 5 & 6 "sleep" means hibernate??? Stange because I thought sleep meant what happens when you shut the lid, ie the pulsating light.

1. See my signature

2. To calibrate a portable computer battery:

1.

Plug in the MagSafe Power Adapter and fully charge the battery.

When the battery is fully charged, the light on the MagSafe Power Adapter connector changes to green and the Battery icon in the menu bar indicates that the battery is charged.
2.

Allow the battery to rest in the fully charged state for two hours or longer.

You can use your computer during this time as long as the power adapter is plugged in.
3.

With the computer still on, disconnect the power adapter and continue to use your computer.
4.

When you see the low battery warning, save your work and close all applications. Keep your computer turned on until it goes to sleep.
5.

After your computer goes to sleep, turn it off or allow it to sleep for five hours or longer.
6.

Connect the power adapter and leave it connected until the battery is fully charged.

You can use your computer during this time.

This is directly from apple. I HAVE to assume the reason you need to turn off the computer, or let it sit for 5 hours, is to finish FULLY draining the battery. I know when I do it, and it goes to hibernate, if you then hold down the power button you can hear the computer FULLY shutdown....

I'm not a master at the exact battery specifics, but to me, if you need to shut it of (or just the fact that you CAN shut it off) or let it sit for 5 hours, means there is still some charge left in the battery, it's just not enough to power the computer or enough to keep the image no the RAM... which is why your image is written to your HDD.

 

[millerb7]

So you are saying in steps 5 & 6 "sleep" means hibernate??? Stange because I thought sleep meant what happens when you shut the lid, ie the pulsating light.

Maybe I'm completely wrong on this then I don't use "safesleep" (osx's hibernate) at all, so I'm not "up to par" on it full. I did pull this off the web maybe it will help....

I was considering 5 & 6 safe-sleep because to me, the machine doesn't have enough power to wake up on it's own, so I was thinking it would be waking from the HDD image... maybe I'm off.

Anyways, for me, I set hibernatemode to 0 and erase my sleepimage and only use normal sleep.

Sorry if I seem to be confusing things I have it all in my head just can't spit it out properly.

Standby puts your computer into energy-saving mode, where it uses very little power.

Hibernate saves your workspace (all your open windows), then turns the computer off.

The difference is that hibernate saves more energy because the computer goes off completely, but it takes longer for the computer to wake up from hibernation, so it's not as convenient.


Sleep is more complicated, because it means different things on different computers.

* Mac OS, desktop. Sleep is the same as Standby. There is no built-in way to Hibernate.
* Mac OS, laptop. Sleep initially means Standby, but if the battery level drops very low then the laptop automatically Hibernates. See below for more on this.
* Windows Vista. Sleep initially means Standby, but it switches to Hibernate if the battery level drops too low (laptop) or the computer has been sleeping for more than three hours (both desktops & laptops). You can change the 3-hour period to something else in Settings > Power Options.
* Windows XP. ???


Hibernate on Mac OS ("Safe Sleep")

Apple calls Hibernation "Safe Sleep". That's what I'll call it too for the rest of this article.

Apple doesn't see fit to let the user choose Safe Sleep on their computers. Safe Sleep happens on laptops only if it's sleeping and the battery level drops too low, and even then only on PowerBooks made after October 2005. You can override that behavior and get your Mac (laptop or desktop) to Safe Sleep immediately on demand with software like Deep Sleep, SmartSleep, or SuspendNow (or see the hacks at Mac Simple Life or MacWorld).


Which should you use: Standby, Hibernate, or Shut Down?

You probably want Standby, because it's the most convenient. With Standby it takes only a few seconds for your computer to wake up. With Hibernate or Shut Down, you have to wait 30 seconds to 3 minutes for it to start up again.

Hibernate or Shut Down will save more energy, but not much. Six watts x 23 hours a day x 30 days a month is 4.1 kWh, which at 15¢/kWh would cost you 62¢/mo. If that kind of savings is important to you, then sure, hibernate or shut down your computer. Otherwise, just set your computer to standby so that it wakes up quickly the next time you want to use it, and don't worry about the very small difference in energy use.