Bios power: Power Management Settings — BIOS for Beginners

Power Management Settings — BIOS for Beginners

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This area of the BIOS seems to be the most misunderstood. When these settings are not properly configured, the result can be systems that do not shut down correctly, or that enter or awaken from the Standby or Hibernate modes improperly. Since Windows has built-in power management, you’ll want to disable all power management in the BIOS. Otherwise, the two fight with each other, and neither works properly. Motherboard manufacturers don’t assume that everyone is using Windows, so many of these settings exist for non-Windows users.

ACPI Suspend to RAM : ACPI stands for Advanced Configuration and Power Interface — not to be confused with APIC or IPCA, which some people may find as options in their BIOS setup programs. The Suspend to RAM feature, sometimes referred to as S3/STR, lets the PC save more power when in Standby mode, but all devices within or attached to the computer must be ACPI-compliant. Some BIOS’s offer an S1/POS option for this scenario. If you enable this feature and experience problems with the standby mode, simply go back into the BIOS and disable it.

Video Off Method : The DPMS (Display Power Management System) option allows the BIOS to control the video display card if it supports the DPMS feature. The Blank Screen option simply blanks the screen — use this for monitors without either power-management or «green» features. The V/H SYNC Blank option blanks the screen and turns off vertical and horizontal scanning. If your computer and monitor were built within the last four years, I recommend setting this to DPMS.

HDD Down In Suspend : This feature determines whether the hard-disk drive is automatically shut down when the computer enters Suspend mode. While most power settings of this type are controlled within Windows, if you find the hard drive is not powering down when the computer enters Suspend mode — assuming your computer even allows Suspend and Hibernate modes — then enable this option. Otherwise, the recommended setting is Disabled.

PWR Button < 4 Secs : By default, all ATX computers will power off after the power button is held for more than four seconds. This setting tells the computer what to do if the power button is held down for less than four seconds. The options are to power off the system or enter Suspend mode. This setting is up to you.

Power Up On PCI Device : If you use Wake-On-LAN — typically employed in large office environments to turn on computers for remote administration — you will want this setting Enabled. Otherwise, I recommend you set it to Disabled.

Wake/Power Up on Ext. Modem : This setting tells the computer to turn itself on when a phone line plugged into its modem rings. Once again, this is used for remote administration. For other environments — in other words, most users — I recommend you set this to Disabled.

Automatic Power Up : This feature, if enabled, lets you designate a specific time each day when the PC will turn itself on. If that’s useful to you, set it to Enabled. Otherwise, I recommend Disabled.

Time (hh:mm:ss) of Alarm : This field sets the time for automatic power-up, based on a military/24-hour clock. The Automatic Power Up field must be enabled to use this feature.

AC Power Loss Restart : This option lets you tell the PC what to do when power is restored after an unexpected loss of power. Disabled leaves the system off, while Enabled reboots the system. Previous State sets the system back to the state it was in before the power interruption. I recommend you set this to Disabled.

Power On By PS/2 Mouse : When enabled, this feature allows the use of a PS/2 (not USB) mouse to turn on the system. Disabled is recommended, so you don’t accidentally keep turning on your computer.

Power On By PS/2 Keyboard : When enabled, this feature lets specific keys on a PS/2 keyboard be used to turn on the system. Disabled is recommended, as most people find this of an annoyance when they accidentally press the wrong key.

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Power Management Settings

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Power management settings in Windows 10 (and BIOS)

Ask Question


3 years, 5 months ago

7k times

I always found the power management settings and energy saving options very confusing since there are more than one.

The first one being the dialog you can open from your taskbar. There is no information at all what those profiles do and how they affect performance, display brighness, etc.:

Also, there is this next window. Where weirdly enough I can’t select the three profiles from the taskbar, but one. Does this mean is is not related to the profiles in the taskbar at all?

Now it gets really confusing as I can modify the profiles from the previous dialog to be more specific. Here I can set when to power off the monitor or even how much CPU-Performance I want.

So now I wonder, what happens if I set my CPU-Performance to max and my profile in the taskbar to the lowest setting? What wins? Does it affect one another? And why is it so hard to find information on this? It feels so basic.

Bonus points if someone can to me explain how this is also all affected by the BIOS settings. If my BIOS-settings are wrong, can it be that 100% performance, is not really 100%?

Of course there are also settings in the driver of my laptop’s manufacturer. But I’ll skip that for now.

Thank you so so much.

  • windows
  • windows-10
  • bios
  • power-management
  • energy-saving


There is not much overlap here between the BIOS and Windows as regarding performance.

The setting you see in the BIOS is only for turning on/off the CPU option of the
Enhanced Intel Speedstep® Technology.

This technology is built into the CPU, not under the control of the OS,
and it allows the CPU more freedom when dynamically adjusting
processor voltage and core frequency.
Its aim is to decrease average power consumption and heat production
by allowing faster and finer control of the performance parameters.

With or without Speedstep, the CPU will adjust automatically its performance,
if it supports boost (and its opposite).
This technology is only advertised as giving faster response time so the CPU
will detect states of less/more usage faster and so will lower/increase its power
consumption faster.
It should be more of importance to large computer centers where power is costly.


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Setting the Setup BIOS to Maximum Performance


It is well known that the performance of your motherboard is highly dependent on the temporary memory settings made in the BIOS Setup. The name of the Setup items in which these temporary parameters are set may vary depending on the chipset and BIOS on your motherboard. Different BIOSes offer the user a different set of options for customizing your system: some (such as Award or AMI) have more than enough options, while others (such as Phoenix) do not provide such options at all. Generally speaking, to achieve maximum performance, you should strive to reduce all time delays. However, setting too small values ​​that are not supported by your system can lead to instability, freezes and inability to boot the computer. However, one should not despair. It is enough to load the Setup defaults after re-entering Setup, and you can be sure that your system will return to its original state. Changing Setup settings cannot damage your system. But the default settings will not provide maximum performance.

This document does not cover the basic issues of interaction with the Setup BIOS, information about which can be found in the documentation for your motherboard. Here is how to overclock your computer without opening the case.

Advanced Chipset Setup

Everything related to time delays and described below can be found in the Advanced Chipset Setup section of your BIOS Setup. The options in this section that affect the performance of your computer are described below.

Auto Configuration

If you want to make any changes to the settings, this option must be disabled. Enabling it leads to the installation of all default time delays, which, as you already know, do not provide maximum performance.

DRAM Read Timing

Keep in mind that the algorithms of the modern Pipeline Burst Cache are designed in such a way that it is much more profitable to perform memory exchanges not in words or bytes, but in groups of four or eight consecutive double words. In terms of timing diagrams, the delay in a memory exchange of several double words looks like x-y-y-y for normal access and x-y-y-y-z-y-y-y for write-back access. Here, the first digit indicates the number of processor cycles required to read the first double word, and the remaining numbers indicate the number of processor cycles required to read subsequent double words. For example, for Pipeline Burst Cache RAM it looks like 3-1-1-1 or 3-1-1-1-1-1-1-1. For conventional main memory, these numbers are not rigidly defined and may vary depending on its type and speed, as well as the advanced user. Therefore, you can use BIOS Setup to change the x, y and sometimes z parameters to increase the performance of the memory subsystem. This suggests the conclusion that in order for the processor to operate faster with memory, you must reduce the above values. Valid values ​​for memory cycles are x222 or x333 for EDO RAM, x333 or x444 for FPM RAM, and x111 or x222 for SDRAM. It is these values ​​that you can change in your Setup. You may have already guessed that SDRAM is the fastest type of memory.

Reduce the waiting times! This will speed up your work. However, keep in mind that when reducing the settings, you should check the stability of the system under multitasking operating systems (for example, Windows 95). Moreover, this check is best performed when actively working with memory. For example, I run two copies of Quake under Windows 95 and switch intensively between them for a while. If everything works, then congratulations.

DRAM Write Timing

This option, which is responsible for the time of writing to memory, is set similarly to the previous one. The only difference to keep in mind is that the latency values ​​for EDO and FPM are set to the same, since the speed of accessing these types of memory differs only when reading (EDO is faster).

As in the previous case, set the smallest possible values. But at the same time, the system must work!

RAS to CAS Delay

It’s rather difficult to make a sensible explanation about this, since the size of my page is limited by the provider.

However, similarly, try to reduce this value, but keep in mind that not all types of memory will work with them. Therefore, do not forget to check the performance of the system in this case as well.

DRAM Leadoff Timing

In short, this is the «x» that was mentioned page back (read/write timing). But setting this value makes a difference between existing chipsets. For example, the maximum that Triton FX can read is 7-y-y-y, while Triton TX or HX allows you to set 5-y-y-y. Therefore, the latest chipsets will run faster. When recording, FX allows you to set 5-y-y-y, and HX and TX can work at 4-y-y-y, but Intel recommends these settings only at an external frequency of 50 or 60 MHz.

As you may have guessed, it is better to set the lowest possible value and check if it works. But the system will only work with a value of 5 if you use memory with an access time of 50ns (or faster) for EDO or 10ns for SDRAM.

Turbo Read Leadoff

Changing this value allows «x» to be further reduced. But the memory that would support this option is quite rare.

You can of course try to enable this setting, but be aware that your system is unlikely to run smoothly, if at all. But if you are lucky, then do not forget to carefully check the performance.

Turbo Read Pipelining

It appears that changing this option changes the «z» in the timing diagram above.

If you want your computer to run fast, try enabling this option as well, although you cannot be sure that the system will run at all.

Speculative Lead Off

When this option is enabled, the DRAM controller may start reading before the address where the requested data is located is completely decoded. This can even speed up memory handling. If this is not the case, then all questions to Novations Technologies Inc.,

Whatever it is, system performance is improved when this option is enabled.

In general, keep in mind that overclocking the memory subsystem is a rather creative thing that is easy to do without knowing anything of what is written above. You just need to download some utility that measures the speed of memory and experiment. However, I hope the suggestions above can help a little.

For more information about other Setup items, see the motherboard FAQ.

This material is a translated and slightly adapted BIOS setup recommendation by Dr. Pabst

November 17, 1999


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Is DAPC really better than BIOS default performance? / Habr

Studying server performance can be very useful, especially if you are working with resource-intensive applications. One way to improve performance is to tweak the BIOS settings. In this article, we will try to answer the question of whether DAPC is really more profitable than BIOS default performance.

Our company is a hoster, and this largely determines the specifics of the work tasks of the DevOps and Support department. However, relatively recently, the usual routine of our work was interrupted by a sudden task: it was necessary to determine whether the use of Performance per Watt (DAPC) in practice allows us to reduce the power consumption of processors and, as a result, the load on the cooling system in the data center.

DAPC (Dynamic Application Power Management) is a BIOS feature that automatically adjusts power consumption depending on the load. That is, when you are not using the server, it will consume less power, which can result in significant power savings. In addition, DAPC can improve server performance in low load mode by running the processor at a higher frequency.

BIOS default performance — BIOS setting that sets the processor to the maximum frequency, regardless of the load. This can improve performance under heavy load, but also increase power consumption and computer temperature.

The differences between the power profiles are detailed in the Dell white paper .

In theory, the choice between DAPC and BIOS default performance depends on your needs. If you want to save energy and improve performance in low load mode, choose DAPC. If you’re looking for maximum performance under heavy load, BIOS default performance is the way to go.

Well, let’s see how it works in practice.

For testing, we used tests stress-ng and AIDA64 .

Test environment

Platform 6


2xXeon 2xE5-2680v2 2.8GHz (10 cores)


8×16 Gb DDR3 REG


1×960 Gb SSD


1xDell PERC H710 Mini

90 127 Mother board



To begin with, we tested the processor:

 stress-ng --cpu 40 --cpu-method matrixprod --metrics --timeout 60 

The test uses 40 CPU threads, the duration of the test is 60 seconds.


real time (secs) 6

BIOS default performance








90 131

Points scored

Points scored

Points scored

BIOS default performance outperformed DAPC in all measured parameters, with the exception of the total test execution time. Bogo ops/s (real time) is a key metric for this test, because this parameter reflects the number of test iterations performed per second and allows you to judge processor performance during testing.

Comprehensive testing

This test measures several key subsystems:

 stress-ng --cpu 40 --io 4 --vm 1 --vm-bytes 128G --timeout 60s --metrics-brief 


90 126


9 0136


bogo ops (secs)

9 0128 real time (secs)

usr time (secs)

sys time ( secs)

bogo ops/s (real time)

bogo ops/s (usr+sys time

BIOS default performance




2192. 06


2619 7.69



















io 84777


16. 14









90 212 0

  • The CPU stressor puts a load on the processor, which allows you to evaluate how well the system copes with computing tasks . CPU stressor-related metrics can include operations per second, execution time, and CPU usage.

  • The IO stressor puts a load on the disk subsystem, which measures how well the system is handling I/O. Metrics associated with an IO stressor can include data transfer rate, I/O time, and other metrics related to the disk subsystem.

  • The VM stressor puts a load on virtual memory, which measures how well the system is doing with memory management and memory page processing. Metrics associated with a VM stressor can include operations per second, execution time, and memory usage.

It is easy to see that these test results are almost independent of the power management method.

Energy comparison

Enabling the Power CAP policy improves the efficiency of workflows in computer systems by setting a maximum value for system power consumption, which helps prevent exceeding the maximum power consumption level and reduces the risk of overheating of components. This is especially important for systems running under high load, such as servers or compute clusters.

For clarity, we have run tests without a power policy and with a 200W limit.

 stress-ng --cpu 40 --io 4 --vm 1 --vm-bytes 128G --timeout 30m 

Without the policy set, the following results were obtained:

Points scored

Points scored

that with a slight decrease in power consumption (308 versus 322 W), DAPC performance is significantly (about 10%) lower compared to BIOS default performance.

We then applied the 200W limit:

Points scored

Processor and component temperatures are important because high temperatures can lead to system overheating and damage to components, and high power consumption can increase the cost of performing work tasks.

The CPU Package shows the total power consumption of the processor. If this value is too high, it may indicate that the processor is under heavy load or that the system needs additional ventilation. Processor core indicators (CPU IA Core) display the temperature of the computing cores. These metrics can help identify problems with individual processor cores, such as utilization, uneven usage, and so on. Using the Power CAP policy can significantly reduce the load on the processor cores (by about 40%).

The processor core voltage (CPU Core Voltages) with and without the Power CAP policy set differs by about 15% (0.912 and 1.086 respectively).

Memory test

 stress-ng --sequential 0 --class io --timeout 60s --metrics-brief 

901 25



9012 6


901 36

9019 7


bogo ops (secs)

real time (secs)

usr time (secs)

sys time (secs)

bogo ops/s (real time)

9 0128 bogo ops/s (usr+sys time)

BIOS aio



162 . 1



81020.07 9aio

17264.35 async I/O signals per sec (average per stressor)












60 9000 6




106232. 02 126






9 0131









90 131






9013 1






793. 88

901 28 BIOS (DAPC)








13450.88 async I/O signals per sec ( average per stressor)











901 31

131. 69




6 0













60.01 900 06





9013 1



60. 04


901 31









The aio (asynchronous I/O) stressor in stress-ng creates asynchronous I/O operations to test the health of the system under high input load conditions -conclusion. These operations include reading and writing files, sending and receiving network packets, and other actions that require I/O. In the test, the result of BIOS default performance significantly exceeds BIOS (DAPC) for each of the test indicators.

The aiol, hdd, rawdev, readahead, revio, seek and sync-file stressors in stress-ng are designed to stress various system components and test their performance under high load conditions.

  • The aiol stressor generates asynchronous I/O to test system health under high I/O load.

  • The hdd stressor puts stress on the hard drive, for example by creating random file accesses or reading and writing large amounts of data to the drive.

  • The rawdev stressor places stress on I/O devices such as block devices or virtual memory devices.

  • The readahead stressor places a load on the file reader subsystem, for example by reading large amounts of data from the file system.

  • The revio stressor creates an I/O load using random file access and reverse file read/write.

  • The seek stressor puts a load on the file read/write subsystem using random file access and movement of the pointer within the file.

  • The sync-file stressor puts a load on the file system by creating a large number of files and reading/writing them.


The tests carried out do not confirm the thesis of DELL platform manufacturers about significant energy savings when using the BIOS (DAPC) mode: system performance is reduced when this mode is selected, and power consumption is reduced slightly.

However, on some Dell servers, using DAPC BIOS mode may result in instability and system crashes. This is due to the fact that the BIOS DAPC mode cannot always correctly assess the load on the processor and correctly adjust its frequency and voltage. As a result, the processor may operate at a low frequency, resulting in slower system performance.

Other power management technologies such as Intel SpeedStep or AMD PowerNow can be used in place of the DAPC BIOS, which can provide more stable system performance and optimize processor power consumption. Note that it is better to update the server BIOS to the latest version. This will avoid bugs and compatibility issues.

In general, the choice of power management technology for a server depends on the specific server model and configuration, as well as performance and energy efficiency requirements. The decision on the choice of technology should be made only after studying the manufacturer’s recommendations and testing on a specific system.