What is Wake on LAN?

Here comes the last part of our small series about switching on and off a (Mini) PC. After talking about ACPI and the Power Button we now take a closer look at Wake on LAN.

As the name suggests, "Wake on LAN" (short: WOL) describes a standard to start a PC via the built-in network card. This can be done on the one hand via the local network, on the other hand, WOL offers the opportunity – and here comes the great advantage – to turn on the computer via Internet.

 

What are the requirements for Wake on LAN?

 

A prerequisite for Wake on LAN is that both, the motherboard and the network card, support the WOL standard. In addition, ACPI or at least its predecessor APM must be activated in the BIOS and the PC should run a current version of Windows, Linux or Mac OS. With Wake on LAN, a computer can be awakened from the idle states S3 (Standby/STR), S4 (Hibernation/STD) and S5 (Soft-Off). (In our article on ACPI we have explained the different states in more detail.) However, it is important that the network card is permanently supplied with power via a standby branch of the power supply – even if the PC is switched off. In addition, the computer must be connected to the router via a network cable.

 

How does switching on via Wake on LAN work?

Switching on is done via a so-called "Magic Packet", that is sent to the network card. It contains the hexadecimal value FF six times in succession, followed by the MAC address of the network card, which is repeated sixteen times without pause. This Magic Packet can be sent from another computer on the network. If you are not on site and would like to switch on a PC via Internet, you can use a different PC, a smartphone or even a NAS. Detailed instructions on how to configure a computer for Wake on LAN can be found here.

Please enter these characters in the following text field.

The fields marked with * are required.

More on this topic

4 Jun 2019 Array ( [id] => 423 [title] => What is a power button? [authorId] => [active] => 1 [shortDescription] => Since we already talked about ACPI and the different states of energy a PC can be in, we continue our little series with the power button. How does it work and what alternatives are there? [description] =>

The power button is, as the name implies, a switch that can be used to switch electrical appliances on and off. In computers, such as our Mini-PCs, the functionality is now limited to switching on. Whereas in the past, at Windows 95 and such, we had to wait a few minutes until the PC shut down and could be switched off, this now happens automatically. Only for hard reset during operation – for example if the PC hangs – it is still needed. Since this can cause software problems, we should only do this in an emergency. Depending on the settings in the software, the Power Button can also be used to put the running PC into hibernation.

What does a power button look like?

Unlike the interfaces, for instance, the appearance of the power button is not specified. It can take various sizes and shapes, depending on how it fits the design or is practical. Often, the power button has an integrated LED that lights up to signal that the PC is running.

How does a power button work technically?

The power button has a cable, which is connected to two pins on the motherboard. By pressing the power button, a circuit is closed on the mainboard. At that moment, the power supply receives the signal to supply the computer with power and thus start up.

What advantages does the power button have?

Actually, the power button is a very practical invention. After all, it offers the great advantage that we can easily turn a PC on, and in emergency also off.

What are the disadvantages of the power button?

The disadvantage of the power button is that we always have to be close to the PC if we want to turn it on. In many industrial applications, however, the computer is permanently installed and is not necessarily freely accessible. Luckily, there are other ways to turn on a PC.

What are alternatives to the Power Button?

One alternative is an external power switch, as it is offered for example for our BOX N2930. Using a cable, the power button can be placed outside, while the PC is installed in a cabinet, stele or the like.

Another option is Wake on LAN, which starts the PC via the network card. In addition, a computer can also be started via the keyboard or mouse and thus via USB (Wake on USB). The only requirement for these possibilities is ACPI.

Another example is the ultra-small single-board computer Raspberry Pi. It does not have a power button, Wake on LAN or anything like that (because it does not have a BIOS) but boots, when it is supplied with power. To turn it off, like all the other PCs, it has to be shut down manually.

[views] => 7 [displayDate] => DateTime Object ( [date] => 2019-06-04 09:30:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [categoryId] => 234 [template] => [metaKeyWords] => [metaDescription] => [metaTitle] => [tags] => Array ( ) [author] => [assignedArticles] => Array ( ) [media] => Array ( [0] => Array ( [id] => 4176 [blogId] => 423 [mediaId] => 50318 [preview] => 1 [media] => Array ( [id] => 50318 [albumId] => 23 [name] => Power_Button [description] => [path] => media/image/Power_Button.png [type] => IMAGE [extension] => png [userId] => 56 [created] => DateTime Object ( [date] => 2019-11-07 00:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [fileSize] => 2306649 [width] => 3000 [height] => 2000 ) ) ) [attribute] => Array ( [id] => 420 [blogId] => 423 [attribute1] => NULL [attribute2] => [attribute3] => [attribute4] => [attribute5] => [attribute6] => [digi1Inactivateblogarticle] => 0 [digi1Sponsoredpost] => 0 [digi1Featuredpost] => 0 [digi1Hideblogdetailsite] => 0 [digi1Showleftsidebarblogdetailsite] => 0 [digi1Disablecommentfunction] => 0 [digi1Hideimageslider] => 0 [digi1Relatedblogarticle1] => 421 [digi1Relatedblogarticle2] => 427 [digi1Relatedblogarticle3] => 346 [digi1Relatedblogarticle4] => [digi1Relatedblogarticle5] => [isReference] => 0 [relatedItem] => ) [comments] => Array ( ) ) 1
know-how
What is a power button?
Since we already talked about ACPI and the different states of energy a PC can be in, we continue our little series with the power button. How does it work and what alternatives are there?
2 May 2016 Array ( [id] => 186 [title] => What is BIOS? [authorId] => [active] => 1 [shortDescription] => In the first part of our BIOS-series we explain the terms BIOS and UEFI. We also talk about the tasks of the BIOS and we answer the important question of how to actually get into the BIOS. [description] =>

What is BIOS?

The abbreviation BIOS means “Basic Input/Output System”. It is the firmware of a PC –  A software which is built integrated into the hardware. The BIOS is stored on a small chip in the mainboard of the computer and is always preinstalled. There are motherboards, which also have a second chip, that acts as backup. The BIOS is the link between the software (OS) and hardware components such as hard drives, keyboard, mouse and printer. The navigation in BIOS is only possible with a keyboard.

And what is this UEFI?

The new version of BIOS is called UEFI, which means unified extensible firmware interface. UEFI looks like an operating system, can be controlled by mouse and is capable of executing programs.

What is BIOS responsible for?

The main tasks of the BIOS are a self-test and the initialization of the hardware as well as the communication between the operating system and other components. When a computer is turned on, the BIOS starts and prepares the PC for booting. First it performs the power-on self-test (POST). The computer checks one by one whether the basic hardware components such as CPU and RAM are working properly. If errors are found, the BIOS displays them by specific sounds or on screen, if the graphics have already been tested successfully.

Following this self-test, the booting process starts. For this, the hardware must know from which component it should boot the operating system. The BIOS searches the operating system in the available devices (hard drives, USB, DVD) following a specific order. As soon as it finds software, the PC is booting automatically. The order of the drives, on which to search for the operating system, can be set in the BIOS. For instance if you want to delete the existing OS and install a new one via DVD, it is necessary to set “CDROM” as first boot device. Other tasks of the BIOS are managing date and time as well as the temperature monitoring of the processor and the mainboard.

How do I get into the BIOS?

To enter the BIOS, a certain key must be pressed (multiple times!)  right after  turning on the PC and even before the operating system  is booted. It depends on the manufacturer which key: usually - and also at all spo-books – the BIOS is accessed by pressing the key "F2" or "Del".

[views] => 49 [displayDate] => DateTime Object ( [date] => 2016-05-02 12:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [categoryId] => 234 [template] => [metaKeyWords] => [metaDescription] => [metaTitle] => [tags] => Array ( ) [author] => [assignedArticles] => Array ( ) [media] => Array ( [0] => Array ( [id] => 4590 [blogId] => 186 [mediaId] => 50309 [preview] => 1 [media] => Array ( [id] => 50309 [albumId] => 24 [name] => bios-chip-mainboard [description] => [path] => media/image/bios-chip-mainboard.jpg [type] => IMAGE [extension] => jpg [userId] => 56 [created] => DateTime Object ( [date] => 2019-11-07 00:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [fileSize] => 1396809 [width] => 4301 [height] => 2867 ) ) ) [attribute] => Array ( [id] => 183 [blogId] => 186 [attribute1] => NULL [attribute2] => [attribute3] => [attribute4] => [attribute5] => [attribute6] => [digi1Inactivateblogarticle] => 0 [digi1Sponsoredpost] => 0 [digi1Featuredpost] => 0 [digi1Hideblogdetailsite] => 0 [digi1Showleftsidebarblogdetailsite] => 0 [digi1Disablecommentfunction] => 0 [digi1Hideimageslider] => 0 [digi1Relatedblogarticle1] => 409 [digi1Relatedblogarticle2] => 188 [digi1Relatedblogarticle3] => 192 [digi1Relatedblogarticle4] => [digi1Relatedblogarticle5] => [isReference] => 0 [relatedItem] => ) [comments] => Array ( ) ) 1
know-how
What is BIOS?
In the first part of our BIOS-series we explain the terms BIOS and UEFI. We also talk about the tasks of the BIOS and we answer the important question of how to actually get into the BIOS.
28 May 2019 Array ( [id] => 421 [title] => What is ACPI? [authorId] => [active] => 1 [shortDescription] => We all like to put our PC into hibernation instead of always shutting it down right away. But how does this work? ACPI makes it possible. Let’s take a closer look at this standard. [description] =>

ACPI is the abbreviation of "Advanced Configuration and Power Interface" and describes an open industry standard for power management of PCs, laptops and servers. In order to use ACPI, an ACPI compatible hardware (motherboard, power supply etc.) and an ACPI compatible operating system (for example Windows) are both required. ACPI was released in 1996 and is being developed by Intel, Microsoft, HP and other IT-companies. The control over the power management lies in the operating system. It has a better overview of the power requirements of the computer and the possibilities to save energy than the BIOS. In contrast to its predecessor APM, with ACPI the BIOS only has the task to communicate with the hardware.

What is APM?

APM stands for "Advanced Power Management". The term also describes a standard for energy-saving methods for PCs. APM was developed by Intel and Microsoft in the early 1990s. The power management features of this standard are mostly managed by the BIOS and hardware. However, since the appearance of ACPI, APM has played only a minor role.

How does ACPI work?

To better understand how ACPI handles power management, we need to go further and look at the different states in which a computer with ACPI can be. The so-called G-state describes four possible states: the mode "G0" designates the active state ("Working"), in which one can work, "G1" the sleep state, "G2" is the so-called "soft-off", a PC with ATX standby voltage, while "G3" describes the unplugged computer ("Mechanical off"). In the case of the "G1" state, you can now distinguish between the various sleep states (s-states):

  • S0: Working – The system is switched on, functional and fully operational.
  • S1: Sleep – Simple sleep mode in which the CPU is stopped.
  • S2: Deeper Sleep – Extended sleep mode, where other components such as the cache of the CPU are turned off.
  • S3: Standby Mode – Much of the motherboard’s hardware is turned off. This mode is also referred to as "Suspend to RAM" (STR) or "Suspend to Memory" (STM), that is, the operating state is still stored on a volatile memory (RAM).
  • S4: Hibernation – Also "Suspend to disk" (STD) – that is, the operating state is backed up to non-volatile memory (hard disk or SSD). The system can be disconnected from the power.
  • S5: Soft-Off Mode – System is switched off (shut down), only the power supply provides power. The system can be activated via a power button or optionally via Wake on LAN.

In addition to the G and S-states, a further distinction is made between ten different CPU states (short "C-states") and five possible device states (short "d-states".

What are the Advantages of ACPI?

The advantage of standby and hibernation is, that the PC does not have to reboot completely and is ready for use more quickly. During these modes, we can also keep programs and files we are working with, open.

[views] => 34 [displayDate] => DateTime Object ( [date] => 2019-05-28 10:30:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [categoryId] => 234 [template] => [metaKeyWords] => [metaDescription] => [metaTitle] => [tags] => Array ( ) [author] => [assignedArticles] => Array ( ) [media] => Array ( [0] => Array ( [id] => 4174 [blogId] => 421 [mediaId] => 50307 [preview] => 1 [media] => Array ( [id] => 50307 [albumId] => 24 [name] => ACPI [description] => [path] => media/image/ACPI.png [type] => IMAGE [extension] => png [userId] => 56 [created] => DateTime Object ( [date] => 2019-11-07 00:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Berlin ) [fileSize] => 2095583 [width] => 3000 [height] => 2000 ) ) ) [attribute] => Array ( [id] => 418 [blogId] => 421 [attribute1] => NULL [attribute2] => [attribute3] => [attribute4] => [attribute5] => [attribute6] => [digi1Inactivateblogarticle] => 0 [digi1Sponsoredpost] => 0 [digi1Featuredpost] => 0 [digi1Hideblogdetailsite] => 0 [digi1Showleftsidebarblogdetailsite] => 0 [digi1Disablecommentfunction] => 0 [digi1Hideimageslider] => 0 [digi1Relatedblogarticle1] => 423 [digi1Relatedblogarticle2] => 427 [digi1Relatedblogarticle3] => 429 [digi1Relatedblogarticle4] => [digi1Relatedblogarticle5] => [isReference] => 0 [relatedItem] => ) [comments] => Array ( ) ) 1
know-how
What is ACPI?
We all like to put our PC into hibernation instead of always shutting it down right away. But how does this work? ACPI makes it possible. Let’s take a closer look at this standard.