Sleep Or Hibernate?

Don Bradbury looks at the theory and practice of energy saving

Actually, energy saving is just one reason why you might want to avail yourself of the Sleep or Hibernate modes your PC claims to support. Other possible reasons include reducing wear and tear on certain components, or reducing noise levels in your working environment, or simply keeping prying eyes off your system while you leave the desk.

But energy saving is the usual reason for using these partial power-down options. When you figure how many PCs are running at any one time around the world, each consuming their, say, 250 watts of power, the potential global savings to be made are huge.

Basic

The simplest form of power saving is to simply switch off the monitor. That taxes the display electronics more than is desirable if you have to engage the mode several times a day. Going into a standby mode of minimal power usage is rather better. If you combine that with a reduction in the power fed to disk drives and processing units etc, more useful saving are to be had. Enter, stage left, the Sleep or Hibernate modes which most modern PCs - at least nominally - support.

I say 'nominally' because you may have difficulty making one or the other of them stick on your particular hardware, even though your BIOS and Operating System say they offer support. That can be for a whole raft of possible reasons, some of which we'll come to, but let's delve into it nevertheless.

The downsides

First, let's take a look at the pitfalls, as there are lots of people around who will tell you that powering down PC components is counter-productive because of the effect it can have on component life. Other things being equal, electronic components do like stability of electrical loading and hence running temperature. But an equal number of people will tell you that, these days, the power and other savings you can make outweigh minimal shortening of component life that may or may not occur.

Screen burn, once a certainty if you left a static picture blazing away at full brightness on your monitor for a long time, is now all but a thing of the past. The phosphors on modern monitors do not burn as easily, yet most PCs you see will still engage a screen saver after a few minutes of inactivity.

Many consider that to be counter-productive as the screen saver itself consumes some computing power. Well, something has to keep watch on your system for the inactivity that will activate it - if you get my drift. Not only that, no power is saved by a screen saver since everything has to be kept running in order to power it.

Better, I think, is to switch off the monitor altogether if you intend to leave the computer idle for an hour or two. Anything longer than that and either Standby or Hibernate mode comes into the reckoning.

Standby

Sleep mode, available on Windows 98, ME, and 2000, powers down the monitor to use minimal current, while stopping the disk drives completely, though only after copying the current state of your PC to system RAM. The latter is maintained by a small current flow. If you get a power outage during Standby mode, bang goes any unsaved work because your complement of RAM will lose its charge. However, it is probably the most-used power saving mode.

Hibernation, if your system supports it, copies your present working condition to hard disk before going into the deepest of power saving sleeps, ie no power consumption at all because everything is switched off under software control. That is, of necessity, slower to restart than Sleep as you have to wait for the relatively slow disk drive to restore everything.

Restoration from RAM is much faster and is often the option of choice on a desktop computer, but Hibernate is particularly useful on a notebook because it gives maximum power saving to prolong the use of your precious battery.

However, both Sleep and Hibernate modes can have their problems, failing to wake up properly, if at all, after sleep is induced.

The blame?

PC engineers tend to blame, first, non-compliant peripherals or their drivers. If you have problems, it's certainly worth hunting for a later driver on the manufacturer's website. That's provided you know which piece of gear is to blame.

New power management specs should help. Intel's Instantly Available PC (IAPC) is expected to restore a PC from sleep mode within seconds. But if you make sure the required mode is both supported and set up properly (BIOS and Operating System) the current provisions are reasonable.

I reckon my own PC wakes up from Sleep mode correctly 95% of times. When it doesn't, I restart the machine from the Reset switch. That implies that I routinely save all my work from running apps before engaging Sleep mode, just to be sure. Favourite failure candidates include one or other of the USB peripherals, notably my flash memory card reader, but sometimes the monitor fails to reactivate, or the entire system lacks stability. Yes sir, it's reboot time again!

Wake up.

Activation of wake up from Sleep mode can involve use of the keyboard, the mouse, modem ring, USB Device Wake up, or Resume by Alarm. I generally just hit the Ctrl key or nudge the mouse, when Sleep is reversed within 20 secs or so, including automatic checks on all drives.

Setting your OS power management for power saving modes involves Power Options in Control Panel. You may not see a tab for Hibernation there, in which case just settle for Sleep mode and do a few trial runs. If you hit problems, try for updated software from the manufacturer. Check BIOS settings carefully, and make sure you haven't missed anything in the Windows's setup.

In conclusion

Finally, a visit to Microsoft's Knowledge Base at http://search.support.microsoft.com/kb/c.asp

just might throw light on a specific problem, though I wouldn't hold my breath; the site is simply littered with manufactures workarounds or worse. Until Microsoft and peripherals manufacturers get their act together, using Sleep and Hibernate will remain an inexact science. Until then, good luck. But do give it a try, it can help save the planet - not to mention your bank balance!

 

Don Bradbury