# "It is now safe to turn off your computer", why don't all PC's do that... **URL:** \ **Category:** Factual Questions\ **Created:** [August 1, 2007, 6:32am UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942 "2007-08-01T06:32:08Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [August 1, 2007, 6:32am UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/1 "2007-08-01T06:32:08Z")
When I shut down my PC at home, the computer runs through its shutdown routine, then after a while, a message box comes up on the otherwise blank screen, that reads: “It is now safe to turn off your computer.” At which time I turn off the computer. **kaylasmom** ’s computer doesn’t do this; it simply runs through the shutdown routine and and turns off. Michaela’s computer does wha her mom’s computer does. So does my computer at work. Well, more precisely, the computers that power down on their own _do_ display the message, but only for an _augenblick_, then they turn off. My computer can keep that message up on the monitor indefinitely. I’m running Windows 2000 on a Pentium III (-type) processor. Michaela has Windows 98 on a Pentium II. **Kaylasmom** and my work computer run Windows XP. What is it that allows some computers to turn off their power supplies, while others require that last bit of human intervention to power down? Is it something in the BIOS? Is it something specific to the motherboard? Is a special power supply necessary to have that feature? Is it a utility? Thank you to anyone who comes in to teach me… ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [August 1, 2007, 6:45am UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/2 "2007-08-01T06:45:51Z")
Older PCs cannot power themselves off and so (ideally) put up that message, newer ones can so they don’t need the message. It’s a feature of both the hardware and OS called [Advanced Configuration and Power Interface](Advanced Configuration and Power Interface) (ACPI). ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [August 1, 2007, 7:10am UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/3 "2007-08-01T07:10:06Z")
[QUOTE=Askance] Older PCs cannot power themselves off and so (ideally) put up that message, newer ones can so they don’t need the message. It’s a feature of both the hardware and OS called [Advanced Configuration and Power Interface](Advanced Configuration and Power Interface) (ACPI). [/QUOTE] Thanks for the response, **Askance**. BTW, in looking at your coding, I note that there are less cumbersome ways to code text for underlining. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 1, 2007, 11:15am UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/4 "2007-08-01T11:15:06Z")
\>What is it that allows some computers to turn off their power supplies, while others require that last bit of human intervention to power down? More specifically, one thing is whether there is a relay or other power modulating component in the power supply. Older computers used a mechanical switch, and no software in the world can reach out of the box and grab something. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [August 1, 2007, 12:16pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/5 "2007-08-01T12:16:04Z")
[QUOTE=kaylasdad99] Thanks for the response, **Askance**. BTW, in looking at your coding, I note that there are less cumbersome ways to code text for underlining. [/QUOTE] His text is coded for a weblink, not underlining. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [August 1, 2007, 12:52pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/6 "2007-08-01T12:52:25Z")
AT power supplies require you to push a power switch. ATX supplies can be shut down by motherboard software. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [August 1, 2007, 3:07pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/7 "2007-08-01T15:07:31Z")
It’s been that way on the Macintosh since 1987 or thereabouts: beginning with Mac System 4 (the first MacOS that was really intended to boot from a hard disk as well as a floppy), if you were on a Mac with an actual physical power button like the SE, on shutdown you’d get the message “It is now safe to power off your computer” (the wording was gradually modified in successive versions); whereas if your Mac used the keyboard’s power button to turn on, like the Mac II, shutting down would simultaneously kill the power and you would not see the message. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [August 1, 2007, 4:20pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/8 "2007-08-01T16:20:28Z")
[QUOTE=AHunter3] It’s been that way on the Macintosh since 1987 or thereabouts: beginning with Mac System 4 (the first MacOS that was really intended to boot from a hard disk as well as a floppy), if you were on a Mac with an actual physical power button like the SE, on shutdown you’d get the message “It is now safe to power off your computer” (the wording was gradually modified in successive versions); whereas if your Mac used the keyboard’s power button to turn on, like the Mac II, shutting down would simultaneously kill the power and you would not see the message. [/QUOTE] Ah, yes, my first Macintosh. An SE running System 6 with 1MB of RAM and a whopping 20MB hard drive. The Macs have always been about the human interface, and so it was no surprise that during shutdown, the message would be, “You may now switch your Macintosh off safely”. This use of “may” always felt like someone dragging their nails on a blackboard. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [August 1, 2007, 5:50pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/9 "2007-08-01T17:50:21Z")
[QUOTE=1920s Style “Death Ray”] His text is coded for a weblink, not underlining. [/QUOTE] Whoosh, I think. Because he a.) didn’t put quotes around the target, and b.) didn’t put an actual url in the target, the ultimate effect was to simply underline the text between the tags. I presume he was intending to link to a wikipedia article on the subject, like this: [Advanced Configuration and Power Interface](http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface). No big deal, I was just having some fun. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [August 1, 2007, 6:39pm UTC](https://boards.straightdope.com/t/it-is-now-safe-to-turn-off-your-computer-why-dont-all-pcs-do-that/413942/10 "2007-08-01T18:39:48Z")
Wooshed ☹