How do wake timers work?












2















Windows most commonly places a computer in S3 (standby/save-to-RAM) mode, where power is cut from the CPU but not to RAM.



If power is cut to the CPU, then how are wake timers triggered? Which component knows when to automatically wake the computer up?



If it is in the BIOS, how does Windows inform the BIOS of the next wakeup time?










share|improve this question



























    2















    Windows most commonly places a computer in S3 (standby/save-to-RAM) mode, where power is cut from the CPU but not to RAM.



    If power is cut to the CPU, then how are wake timers triggered? Which component knows when to automatically wake the computer up?



    If it is in the BIOS, how does Windows inform the BIOS of the next wakeup time?










    share|improve this question

























      2












      2








      2








      Windows most commonly places a computer in S3 (standby/save-to-RAM) mode, where power is cut from the CPU but not to RAM.



      If power is cut to the CPU, then how are wake timers triggered? Which component knows when to automatically wake the computer up?



      If it is in the BIOS, how does Windows inform the BIOS of the next wakeup time?










      share|improve this question














      Windows most commonly places a computer in S3 (standby/save-to-RAM) mode, where power is cut from the CPU but not to RAM.



      If power is cut to the CPU, then how are wake timers triggered? Which component knows when to automatically wake the computer up?



      If it is in the BIOS, how does Windows inform the BIOS of the next wakeup time?







      sleep wake-up






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Aug 2 '15 at 19:20









      oldmud0oldmud0

      3,11631536




      3,11631536






















          2 Answers
          2






          active

          oldest

          votes


















          2














          This is done via the "alarm" registers in the RTC (real-time clock). On the original PC-AT, this chip was a Motorola MC146818.



          Before going to sleep (ACPI S3), the kernel will program the next-scheduled wake-up time into the "alarm" registers on the RTC, which is always powered-on. When this wake-up time arrives, the RTC will trigger the chipset to power-on the system, and resume from S3. (Note that in most modern systems, the RTC is actually part of the southbridge itself, so the power-on signalling happens internally).



          After the system resumes from sleep, the kernel will evaluate its list of pending wake events, dispatching the ones that have arrived.



          This paper from Intel describes the interface (for x86 systems):





          • Accessing the Real Time Clock Registers and the NMI Enable Bit


          The programming of these registers is done in the Linux kernel in cmos_set_alarm.






          share|improve this answer

































            0














            A wake timer is a timed event that wakes the PC from sleep and hibernate states at a specific time. For example, a task in Task Scheduler set with the "Wake the computer to run this task" check box checked.



            Important wake timers are a new class of wake timer in Windows 10 that includes things like reboots after a Windows update that requires one. They supersede all other settings.



            This tutorial will show you how to enable or disable to allow wake timers to wake the computer in Windows 10.



            To Enable or Disable Allow Wake Timers in Power Options




            1. Open the advanced power settings of a power plan you want to enable or disable wake timers for.


            2. Expand open Sleep and Allow wake timers. Select Enable, Disable (default on battery), or Important Wake Timers Only (default plugged in) for what you want, and click/tap on OK.







            share|improve this answer
























            • You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

              – Scott
              Jan 19 at 9:35











            Your Answer








            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "3"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            autoActivateHeartbeat: false,
            convertImagesToLinks: true,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: 10,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














            draft saved

            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fsuperuser.com%2fquestions%2f949540%2fhow-do-wake-timers-work%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            2














            This is done via the "alarm" registers in the RTC (real-time clock). On the original PC-AT, this chip was a Motorola MC146818.



            Before going to sleep (ACPI S3), the kernel will program the next-scheduled wake-up time into the "alarm" registers on the RTC, which is always powered-on. When this wake-up time arrives, the RTC will trigger the chipset to power-on the system, and resume from S3. (Note that in most modern systems, the RTC is actually part of the southbridge itself, so the power-on signalling happens internally).



            After the system resumes from sleep, the kernel will evaluate its list of pending wake events, dispatching the ones that have arrived.



            This paper from Intel describes the interface (for x86 systems):





            • Accessing the Real Time Clock Registers and the NMI Enable Bit


            The programming of these registers is done in the Linux kernel in cmos_set_alarm.






            share|improve this answer






























              2














              This is done via the "alarm" registers in the RTC (real-time clock). On the original PC-AT, this chip was a Motorola MC146818.



              Before going to sleep (ACPI S3), the kernel will program the next-scheduled wake-up time into the "alarm" registers on the RTC, which is always powered-on. When this wake-up time arrives, the RTC will trigger the chipset to power-on the system, and resume from S3. (Note that in most modern systems, the RTC is actually part of the southbridge itself, so the power-on signalling happens internally).



              After the system resumes from sleep, the kernel will evaluate its list of pending wake events, dispatching the ones that have arrived.



              This paper from Intel describes the interface (for x86 systems):





              • Accessing the Real Time Clock Registers and the NMI Enable Bit


              The programming of these registers is done in the Linux kernel in cmos_set_alarm.






              share|improve this answer




























                2












                2








                2







                This is done via the "alarm" registers in the RTC (real-time clock). On the original PC-AT, this chip was a Motorola MC146818.



                Before going to sleep (ACPI S3), the kernel will program the next-scheduled wake-up time into the "alarm" registers on the RTC, which is always powered-on. When this wake-up time arrives, the RTC will trigger the chipset to power-on the system, and resume from S3. (Note that in most modern systems, the RTC is actually part of the southbridge itself, so the power-on signalling happens internally).



                After the system resumes from sleep, the kernel will evaluate its list of pending wake events, dispatching the ones that have arrived.



                This paper from Intel describes the interface (for x86 systems):





                • Accessing the Real Time Clock Registers and the NMI Enable Bit


                The programming of these registers is done in the Linux kernel in cmos_set_alarm.






                share|improve this answer















                This is done via the "alarm" registers in the RTC (real-time clock). On the original PC-AT, this chip was a Motorola MC146818.



                Before going to sleep (ACPI S3), the kernel will program the next-scheduled wake-up time into the "alarm" registers on the RTC, which is always powered-on. When this wake-up time arrives, the RTC will trigger the chipset to power-on the system, and resume from S3. (Note that in most modern systems, the RTC is actually part of the southbridge itself, so the power-on signalling happens internally).



                After the system resumes from sleep, the kernel will evaluate its list of pending wake events, dispatching the ones that have arrived.



                This paper from Intel describes the interface (for x86 systems):





                • Accessing the Real Time Clock Registers and the NMI Enable Bit


                The programming of these registers is done in the Linux kernel in cmos_set_alarm.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Jan 19 at 5:19

























                answered Aug 2 '15 at 19:32









                Jonathon ReinhartJonathon Reinhart

                1,86762650




                1,86762650

























                    0














                    A wake timer is a timed event that wakes the PC from sleep and hibernate states at a specific time. For example, a task in Task Scheduler set with the "Wake the computer to run this task" check box checked.



                    Important wake timers are a new class of wake timer in Windows 10 that includes things like reboots after a Windows update that requires one. They supersede all other settings.



                    This tutorial will show you how to enable or disable to allow wake timers to wake the computer in Windows 10.



                    To Enable or Disable Allow Wake Timers in Power Options




                    1. Open the advanced power settings of a power plan you want to enable or disable wake timers for.


                    2. Expand open Sleep and Allow wake timers. Select Enable, Disable (default on battery), or Important Wake Timers Only (default plugged in) for what you want, and click/tap on OK.







                    share|improve this answer
























                    • You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                      – Scott
                      Jan 19 at 9:35
















                    0














                    A wake timer is a timed event that wakes the PC from sleep and hibernate states at a specific time. For example, a task in Task Scheduler set with the "Wake the computer to run this task" check box checked.



                    Important wake timers are a new class of wake timer in Windows 10 that includes things like reboots after a Windows update that requires one. They supersede all other settings.



                    This tutorial will show you how to enable or disable to allow wake timers to wake the computer in Windows 10.



                    To Enable or Disable Allow Wake Timers in Power Options




                    1. Open the advanced power settings of a power plan you want to enable or disable wake timers for.


                    2. Expand open Sleep and Allow wake timers. Select Enable, Disable (default on battery), or Important Wake Timers Only (default plugged in) for what you want, and click/tap on OK.







                    share|improve this answer
























                    • You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                      – Scott
                      Jan 19 at 9:35














                    0












                    0








                    0







                    A wake timer is a timed event that wakes the PC from sleep and hibernate states at a specific time. For example, a task in Task Scheduler set with the "Wake the computer to run this task" check box checked.



                    Important wake timers are a new class of wake timer in Windows 10 that includes things like reboots after a Windows update that requires one. They supersede all other settings.



                    This tutorial will show you how to enable or disable to allow wake timers to wake the computer in Windows 10.



                    To Enable or Disable Allow Wake Timers in Power Options




                    1. Open the advanced power settings of a power plan you want to enable or disable wake timers for.


                    2. Expand open Sleep and Allow wake timers. Select Enable, Disable (default on battery), or Important Wake Timers Only (default plugged in) for what you want, and click/tap on OK.







                    share|improve this answer













                    A wake timer is a timed event that wakes the PC from sleep and hibernate states at a specific time. For example, a task in Task Scheduler set with the "Wake the computer to run this task" check box checked.



                    Important wake timers are a new class of wake timer in Windows 10 that includes things like reboots after a Windows update that requires one. They supersede all other settings.



                    This tutorial will show you how to enable or disable to allow wake timers to wake the computer in Windows 10.



                    To Enable or Disable Allow Wake Timers in Power Options




                    1. Open the advanced power settings of a power plan you want to enable or disable wake timers for.


                    2. Expand open Sleep and Allow wake timers. Select Enable, Disable (default on battery), or Important Wake Timers Only (default plugged in) for what you want, and click/tap on OK.








                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered Jan 19 at 8:58









                    Bryan GreeneBryan Greene

                    1




                    1













                    • You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                      – Scott
                      Jan 19 at 9:35



















                    • You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                      – Scott
                      Jan 19 at 9:35

















                    You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                    – Scott
                    Jan 19 at 9:35





                    You have defined “wake timer” and given some information on how they are used.   But you have not answered the question: how do they work?

                    – Scott
                    Jan 19 at 9:35


















                    draft saved

                    draft discarded




















































                    Thanks for contributing an answer to Super User!


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    To learn more, see our tips on writing great answers.




                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fsuperuser.com%2fquestions%2f949540%2fhow-do-wake-timers-work%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    Popular posts from this blog

                    Сан-Квентин

                    Алькесар

                    Josef Freinademetz