The Reinvention of the PC Power Switch

In around 1998 or so, I noticed something a bit peculiar that was starting to happen with brand-new PC computers.

At the time, I was still taking PC technical support calls, and every now and then, I would get a customer calling in who needed help installing software, drivers or whatnot for their brand new Pentium PC (running Windows 98, of course). Depending on the extent of changes, rebooting the computer was sometimes warranted. For good measure, performing a "cold boot" was a typical course of action.

In case you are unfamiliar with the term, "cold booting" means to shut down the OS and physically switch off the power of the computer, wait several seconds to let all the internal fans and drives spin down, then switch the power back on (as opposed to warm booting, where you would simply tell the OS to shutdown and automatically restart the computer right away without any power interruption).

Anyhow, the "strange" thing was that some customers would get to the point of shutting down Windows, but then when they went to press the power switch off, they claimed that the computer was frozen, and it would not turn off no matter how many times or how hard they tried pressing the power button... they would literally have to pull the plug out of the wall (or switch off their powerbar) to actually cut the power.

It didn't take me very long to figure out what was happening -- why all these brand new state-of-the-art Pentium computers would simply refuse to turn off...

Before I continue, a little bit of backstory; having used PCs since 1988, all the computers I ever had at home up to that point used the old-school manual toggle-type power switches, which could only physically be in either on or off states. I only had to look down at the workstation that I was using on my desk at work to see an example of these new-fangled computer power switches. Of course, we would hardly ever have much reason to turn off our workstations at work (unless the computer crashed), so this phenomena of "the computer won't turn off", wasn't really something that I had personally experienced or really took very much notice of.

But getting back on track; The cause of all this peculiarity was due to a new industry-standard technology called Advanced Configuration and Power Interface (ACPI). Originally developed as an open-standard near the end of 1996 by a consortium of industry power-players such as Hewlett-Packard, Intel, Microsoft, Phoenix, and Toshiba, it wasn't until around 1998 when many of the major PC manufacturers started putting ACPI into all of the new PCs that they built as a standard feature (presumably so that their systems could meet the required qualifications in order to wear the Windows and Intel compliancy badges).

What the manufacturers didn't really make clear however, was exactly how ACPI changed the way computers are turned on and off. Beyond the basic "push the button to turn it on" concept, which doesn't exactly require a Ph. D. to figure out, and the apparent behaviour that computers can now turn themselves off upon shutting down, perhaps nobody really thought that there was any purpose to explain things much further... after all, if you have a new ACPI-compliant system, why would you be concerned with comparing the process to the old way anyhow? Besides, to most average novice or intermediate computer users, anything beyond the basics would probably just be confusing, intimidating and a plain "turn-off" (sorry for the pun). I would even speculate that any modern computer usage course -- whether it be an introductory computer usage course for absolute beginners, right up to courses for the advanced power user -- probably wouldn't touch on the subject of how to operate the power switch in very much depth.

I'm not saying that nobody has ever documented or explained it properly... some computer manufacturers do in fact provide excellent documentation. However, many people tend not to read their computer manuals, and I have encountered quite a number of people who just couldn't figure out why their computer can not turn off... even people who have a relatively extensive familiarity with computers.

Even though PC power switches have already been working this way for the past decade, laugh as you may, but there undoubtedly are people out there who have gotten stumped by their power switch before. So in case nobody ever told you, you never figured it out, or maybe if you are simply too embarrassed to admit that you didn't know it before... I'll basically sum things up here;

• To turn ON an ACPI-compliant computer, simply depress and release the power switch.
• To turn OFF an ACPI-compliant computer safely, use the shutdown command of your operating system (only if your operating system supports ACPI). The operating system should automatically power off the computer on its own once the shutdown process has completed. You should not have to touch the power switch to turn off the computer.
• If you press the power button while an ACPI-compliant computer is running, depending on how the operating system is configured, any of the following could happen:
• Nothing will happen.
  
• The OS will ask you what you want to do (standby, hibernate, shutdown or reboot).
  
• Put the computer in stand-by mode (turns off certain parts of the computer such as the hard drive and display, puts the CPU in low power mode to save energy).
  
• Hibernate the operating system and power off the computer.
  
• Initiate the operating system shut down procedure and power off the computer.
• Initiate the operating system shut down procedure and immediately reboot the computer.
  
• Immediately power off the computer without initiating a log-off or shut down (this might indicate a problem with the power supply/circuitry, or the OS does not support ACPI).
  
• And finally, the special case: If the operating system has already finished shutting down (or not), and the computer still won't turn off by itself, and pressing and releasing the power switch has no effect, there is no need to pull the power cord or switch the power bar off. All you need to do is hold down the power switch for about 10 seconds, and the computer power will switch off. This can also be done to manually switch off the computer without shutting down the OS in case of emergency or for whatever reason.
• If you have held down the power switch until the computer has turned off, but the computer turns back on immediately after you release the button (I have a older computer that actually does this sometimes), either the OS was unable to set the ACPI interface properly for some reason, or the power supply might be bad and needs to be replaced. In this case, you can either try allowing the computer to boot up completely, then try properly shutting down again (hopefully this will allow the OS to reset the ACPI interface properly), or you may in fact have to pull the power cord in order to shut off the power. The computer should stay off when you plug the cord back in.