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Study of power consumption and features of the computer in various power saving modes

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Most people turn their desktop off when they finish working with a desktop or laptop computer (“shutting down” in Windows). Some keep the computer always on. Well, the remaining minority use power saving modes.



For this study, I was motivated by a desire to find out the power consumption of a computer in sleep and hibernation modes, as well as the recent replicas of owners of solid-state drives that became more frequent, about how quickly their computer and programs are loaded compared to a computer with a hard disk. But first things first.



On ebay, I purchased a household amp WANF (made in China) worth $ 20. As such, the current consumption of this ammeter does not display on the screen, but shows the mains voltage and power consumption. The purpose of this device is to show the power consumption of the equipment included in it.

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Test computer configuration:



The configuration is quite typical for a home work computer.



Let us turn to the actual measurements of energy consumption. Consider the different modes of ACPI



State S3 (Sleep) - 3.5 watts.



In this state, power is supplied to the motherboard and RAM. The processor, video card and other peripherals are disabled. The output of the computer from sleep mode to the operating mode is almost instantaneous and you get a desktop with all running programs in the state in which they were before going to sleep. RAM content is fully preserved, including cached data (Prefetch and Superfetch)

Sleep mode is very convenient for everyday use on the desktop. In the morning turn on the computer - and, voila, you can immediately work. SSD or HDD disk - does not matter, the computer turns on instantly. Since cached data is saved in RAM, restarting applications is very fast with respect to computer cold start, which again levels the speed difference between SSD and HDD.

Energy consumption is so low that daily use of this mode will cost only 10 extra rubles per month for electricity. Wi-Fi router, VoIP adapter and TV in standby mode consume more, 4-5 watts each.



S4 / S5 (Hibernation / Disabled) states - 1.7 W or 0 W , depending on BIOS settings.



Modes S4 and S5 for power consumption are similar. By default, power is supplied only to the motherboard, and the RAM, processor, and other peripherals are disabled. However, in the BIOS settings you can enable deep (Deep) S4 / S5. In this case, the motherboard also turns off and the computer does not consume anything. The disadvantage of this option is that the computer can be turned on only with the power button, while in the first case it can be turned on by the RTC aarm event (for example, Windows Task Scheduler task timer), Wake-on-LAN, pressing a button on the keyboard or mouse, etc.



Read more about the modes themselves. S4 - Hibernation (hibernation) - a mode in which the contents of the RAM are reset to disk (permanent memory) before shutting down the computer. When you turn on the computer, the contents of the RAM is restored from a dump on the disk, and we get the computer in the same state as before the transition to hibernation. In this regard, hibernation is similar to the sleep mode, but the readiness to work does not occur instantaneously, but in about 30 seconds (when using a hard disk as the system drive)

In addition, the cached data from RAM is not saved in the dump, so the launch of applications after returning from hibernation is slow as after a cold start. For the desktop, this mode has no advantages over sleep and is more suitable for laptops.



The S5 state is normal shutdown. Additionally, there is nothing to tell.



For comparison, I will give the computer consumption in the operating mode (state S0).



Consumption in idle time - 95 watts. The first monitor is connected to a discrete Radeon video card, the second monitor is connected to a video card integrated into the processor. If we connect both monitors to a discrete video card, the consumption increases by 30 watts and is 125 watts. Thus, it is better to connect the second monitor to the motherboard. In addition to energy savings, we can use Intel Quick Sync technology, which significantly speeds up (more than discrete video cards) video conversion to H.264. If at least one monitor is not connected to the integrated video, then Quick Sync will be unavailable.



Consumption in benchmarks. No comments required.



I hope this article will help you in saving energy, saving the resource of PC components and making a more balanced choice of using HDD or SDD for your computer.

Source: https://habr.com/ru/post/144179/

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