Power Settings on an Operating System can have different effects on system performance. If you want to use less energy and allow your Laptop to run longer then you would set your Power Settings to save power at the cost of performance. In most cases on a PC or Server, you do not want to have any power savings as you want the max performance you can get out of a system. Power Options are sometimes not set properly after setting up a new Operating System Installation or is overlooked when troubleshooting performance issues. You may have a high end CPU with many cores but for some reason even under light load, the CPU usage is over 50%. In this post I will mainly be looking at the Windows Operating System when it comes to Power Settings and things to look for to make sure that your System is running at it’s peak performance.
The Windows Operating System
By default when you do a fresh installation of Windows 8.1 or Windows Server 2012 R2, if you look at the Power Options in Control Panel, you will notice that it is set at “Balanced” plan. Under normal circumstances for a normal user using a PC this is acceptable. But for a Server that is running performance critical applications, this setting is unacceptable and you should be using the “High Performance” plan. The reason for this is because in the “Balanced” plan, CPU Throttling technologies such as Intel SpeedStep and AMD CoolnQuiet will be taken advantage of by the Windows Operating System in order to lower the CPU frequency based on the current work load in order to save energy. This sounds great on paper but based on experience in a Server Environment, sometimes the CPU Frequencies are still throttled down even though the Server is under a heavy load and are not running at their max frequency.
In this picture below, I am using a program called CPU-Z to display information about the AMD FX-8320 CPU that I use in my desktop. I have set my Power Settings to be in the “Balanced” plan. The normal operating frequency for this CPU is 3.5Ghz with 4 Ghz in Turbo core mode. But you will see that at the moment it is only running at 1.4 Ghz when Idled.
In this picture below, I have set my Power Settings to be in the “High Performance” plan. Now you will see that the CPU is running at 3.7Ghz with Turbo core mode engaging.
Another interesting thing to see is that the Power Settings can dynamically change how fast each CPU Core runs. As you can see in this picture below, by using a program called HWMonitor, I can see that some Cores are running at full speed but some are running at their minimum speed.
The BIOS
If in the Windows Operating System you have set your Power Plan to “Full Performance” but you are still seeing the CPU being throttled, this means that your PC/Server BIOS is overriding the Windows Operating System Power Plan. In most BIOS’s, you can turn off features such as Intel Speedstep / AMD CoolnQuiet or set the Power Performance Profile. On servers, you want to set this at Max Performance in order to guarantee that the CPU and all it’s Cores will be running at their Max CPU Frequency.
Conclusion
If your PC/Server is suffering from performance issues, it is best to first check to see if you have any power saving modes turned on or if it is running under another Power Plan that is not “High Performance”. This can save you some time in troubleshooting and ensuring that your PC/Server is running at its full potential. As you want a Server to be running at its full capacity, you definitely do not want the Server CPU to be throttled especially during critical work hours!