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Hybrid Sleep Mode
Windows Vista introduced a new sleep mode called “Hybrid Sleep.” When a PC goes into hybrid sleep, the PC suspends everything but the RAM. If the system is not used in a while, the PC wakes up and goes into hibernation. Hybrid sleep is thus a very low power mode, but it still allows for a rapid restart, as long as the PC has power supplied to maintain the RAM and not too much time has passed. In the event of an outage in the interval when the computer is sleeping, the contents of RAM will be scrambled, but the computer can still restart, albeit more slowly, by loading the hibernation file. This is still faster than a reboot.
This compares to the two distinctly different power modes offered in Windows XP – sleep (suspend) and hibernate. When selecting sleep, XP would display “Preparing to sleep.” The screen would then blank, the fans would stop, and the hard drive would coast down. Selecting hibernate caused XP to display “Preparing to hibernate.” The user would hear the hard drive spin up to write the contents of memory to the hibernation file. Then the drive and the fans would stop and the PC would shut off.
Hybrid sleep mode can be used on a notebook PC, but the advantage of using it is less than on a desktop. This is because notebooks don’t normally experience power outages. They are able to “wake” themselves and hibernate if the battery level becomes low.
Of course, even simple questions can have complicated answers, so let's look more closely.
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As a side effect, Vista gives the notebook user less information about what the power state is than XP did. Instead of displaying a message about going to sleep or entering hibernation, the screen just blanks as the operation proceeds. The user may think that the process is complete before the hibernation file has been written, and moving the notebook at this time of high hard drive write activity may damage the hard drive.
To prevent this, after selecting Sleep, wait for the hard drive activity LED to go out and for the Sleep LED to illuminate before moving the notebook. This is applicable both when hybrid sleep is enabled and when it is not. Similarly, when selecting Hibernate, wait for the hard drive activity LED to go out and for the Sleep LED to stop flashing before moving the notebook.
In Vista, when your notebook comes out of hibernation, it will return to hibernation if no control input (movement of the mouse or keyboard activity) is made within two minutes. This is an annoying feature in that it prevents the user from, for example, going to start the coffee while resuming from hibernation, and it happens both when on battery and when plugged in. All Vista notebooks seem to do this, so it must have been by design.
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Hybrid Sleep and USB
Another odd effect is seen if hybrid sleep is enabled, the notebook is sleeping, and the user detaches an USB mouse or keyboard. The PC wakes automatically whether you wanted it to continue sleeping or not. You can change this behavior by going to the Properties of the keyboard and mouse in Device Manager. In each case, deselect “Allow this device to wake the computer.”
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And there’s more oddness yet. In XP, if the battery is being expended and eventually reaches the “critical battery level,” the OS warns the user and then either shuts down or hibernates. In Vista, it’s possible for the user to set the critical battery level higher than the low battery level. When this combination is set, Vista will give no warning and will not prevent the user from continuing.
The clues that the notebook has entered this condition are slight and inconsistent. In the system tray, a small white on red “X” appears superimposed to the left side of the battery icon. If the user opens up the Windows Mobility Center, the “Battery Status” in this condition has a yellow triangle with a black exclamation point. I guess the system tray guys and the mobility center guys weren’t communicating when this was designed.
The solution here is simply not to set the critical battery level higher than the low battery level. To check, click the Start button, type in “Power Options,” and press Enter. Then click on “Change plan options” under the selected power plan. On the next dialog, select “Change advanced power settings.”
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Hybrid Sleep Power Options
This will open the Power Options dialog for the selected plan. We’re interested in the settings under “Battery,” specifically “Low battery level” and “Critical battery level.” Using the “Power Source Optimized” power plan, the settings for this on my ThinkPad are:
Low battery level
- On battery: 20%
- Plugged in: 10%
Critical battery level
- On battery: 7%
- Plugged in: 5%
I think this is a reasonable combination of settings. If the battery gets low, I expect a notification long before it becomes critical. If I need to continue working and am being unreasonably stubborn about it, I expect that the notebook will take over and save my work before the battery completely expires. 7% for the critical battery level is reasonable because it will still have enough power to hibernate.
For “Critical battery action,” I have the ThinkPad set to hibernate. Other options are Sleep (not such a good idea if hybrid sleep is enabled and the battery is this low) and Shut Down (which may be pretty ragged and cause the user to lose his work).
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Vista Hibernation Problems
In XP, it was not uncommon for hibernation to fail. Some users had the unpleasant experience of pulling their notebook out of their bag and discovering that it was dead because XP got hung up for whatever reason and failed to hibernate. In a like vein, pulling the notebook out and finding it both warm and still running was not uncommon.
Vista is much better about this. When sleep or hibernate is selected, the OS sends a shut-down signal to each application and service and then gives them five seconds to clean up, save what they need to, and terminate. If the application or service does not comply, Vista shuts them off automatically.
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Vista Power Defaults
Microsoft doesn’t want to have us curl our thoughts around what hibernation, sleep, on, and off actually mean. This is a quote from Jim Allchin on the official Windows Vista Blog:
“I strongly encourage you to use the defaults in Windows Vista. And no need to think much anymore about different power-saving modes and terms like hibernate, sleep, etc. – just hit the symbol for “on” and “off” and let the system do the thinking and power saving for you.”
Kudos to the team. Some thinking really went into power management, especially on the desktop, where Vista shines. (But Jim, we Bright Hub writers and readers prefer to do our own thinking.)
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Windows Vista Hybrid Sleep
So is it worthwhile to enable and use hybrid sleep on a Vista notebook?
Yes, it won’t hurt anything.
Some users will immediately decide that sleep means sleep and hibernate means hibernate and will disable hybrid sleep as soon as they can. I’m leaving it enabled on my notebook because of those times when I pulled my old XP ThinkPad out of the sleeve and found it warm or dead. It’s a bit of a mixed bag, but if I put the notebook to sleep and forget about it, it’s nice that Vista will notice and hibernate the machine well before the low or critical battery level happens.
That said, I did not get hybrid sleep working well right away. The ThinkPad was losing 24% of the battery overnight when set to sleep. Something was waking it up during the night. First, I tried disabling “Allow this device to wake the computer” for the wireless network adapter in Device Manager. That had no effect. Then I noticed that Windows Update was set to go off at 3:00 am. Changing that improved things, but the battery still went down more than I thought it should.
Ultimately the problem turned out to be Kaspersky Antivirus. I set it to check once per day at 10 a.m., and the ThinkPad made it through the night with 100% battery.
I still select Hibernate when I know it’s going into the bag for a day or two, but I select Sleep if I think I may return to the notebook within an hour or two. In the last almost a year that I've had this ThinkPad, I haven’t had the notebook hang up once when going into sleep or hibernation mode, and for that, I’m quite pleased.
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