Sleep Mode

Sleep mode is a low power mode for electronic devices such as computers and is used when a device is idle. Sleep mode saves electricity as less power is required during sleep mode than in normal operations. This is commonly archived in laptops by turning the screen off after a period of inactivity and in desktop PC's monitors will turn off after a period of time. More recently more advanced power management as been introduced including the ability to turn of hard drives and to save the RAM to hard disk (Hibernation).

Advanced Configuration and Power Interface (ACPI) specification is an open industry standard first released in 1996 developed by HP, Intel, Microsoft, Phoenix and Toshiba that defines common interfaces for hardware recognition, motherboard and device configuration and power management.
Another important feature of ACPI is in bringing power management features previously only available in laptop computers to desktop computers and servers.
Like the ability to put systems into extremely low consumption states in which only memory is powered this is the highest level of sleep mode.

In hibernation not even the memory is powered as it is stored on the non volatile hard disk. Interrupts which can be sent by devices such as the keyboard can quickly wake the system.ACPI requires compliant hardware and therefore cannot be applied to older hardware. The operating system, motherboard, chipset and for some functions even the CPU, must be designed with support for it. For example Intel Core 2 Duo processors can run in low power modes but not all processors can cope with this.

ACPI uses its own ACPI Machine Language (or AML) for implementing power event handlers, rather than the native assembly language of the host system this makes it a third generation language and processor independent. The AML code is part of firmware (BIOS), but is interpreted by the operating system such as Windows Vista or Ubuntu Linux.

The first version of Microsoft Windows to support ACPI was Windows 98. All distributions of Linux have at least some support for ACPI. But some are better than others.

I think this technology could be developed in the future to detect what the user is doing and adjust the power scheme accordingly to save on battery power when the user is not doing anything requiring full power. This could also be done on desktop PC's to save on power consumption and this could be put to even better use on servers. They are rarely turned off but are not used at full capacity for a lot of the time. with the ACPI now available to servers significant savings in power consumption could be made saving the environment and companies energy bills.

It must be remembered that sleep mode is not the same as a screen saver. Most monitors consume only a few watts in sleep mode. In contrast, screen savers can use as much electricity as if the computer monitor were in full use.

I feel this is personally relevant to me because I have a passion for technology and for the environment. I am also a big user of sleep mode and hibernation with my laptop at university as it prolongs battery life and allows for quicker startups. I have set my Vista laptop to turn the screen off after 1 minute of inactivity and this extends the battery life enormously. I can also reduce the performance of my machine to further extend battery life but this is fine for word processing and internet use.

Other possible reasons for using sleep mode or hibernation include reducing wear and tear on certain components such as processors, or reducing noise levels in the working environment as fans will not need to be running and air conditioning would not be needed to extract the heat from the room as is found in many offices. Air conditioning and refrigeration are two of the biggest consumers of electricity in the world

But energy saving is the usual reason for using sleep mode. When I think how many PCs are running at any one time around the world, millions of them and each consuming over 300 watts of power or more , power supply units just keep getting bigger to cope with the new generation of hardware, multi core processors and high specification graphics cards all consume a lot of electricity and a lot of this power isn't used productively. If everyone used sleep mode and hibernation the amount of energy that could be saved is huge and could have a significant impact on the rate of climate change as less power needed would result in less fossil fuels having to be burnt.

I plan to do further research and find out accurate figures for the consumption of power from computers and show the effect that sleep modes and hibernation have on reducing energy demand. I may even do some primary research using my own laptops to see the difference. But I feel a combination of primary and secondary sources would provide the outcome. I plan to do most of my research online as this is a fairly new topic there are unlikely to be many books on this subject.

I think that this technology has real potential for use in server technology and data centres as well in other areas of electronics such as Television and even games consoles. It would be a good feature to be able to pause a games console and reduce the power consumption whilst it is not in use.