BurnInTest - What duty cycle setting should I use

There is some confusion between 100% duty cycle and 100% CPU load. The duty cycle setting in BurnInTest determines how quickly the various tests in BurnInTest run. Using a duty cycle value of less than 100% means short pauses are inserted into the test. 100% means a tight testing loop, with no pause. The duty cycle value does not necessarily equal the percentage load value displayed in Windows task manager. It might seem like a good idea to run all the tests at the same time and wind up all the tests to 100% duty cycle. But it isn't.

Imagine you have one application running on a computer that uses 100% of the CPU time. Adding a second instance of the same application (which could also potentially use 100% of the CPU time as well) doesn't increase the load on the machine. You can't have 200% CPU load. It's impossible. So by running more tasks, you aren't increasing the load, instead the operating system puts more and more tasks into a sleep state as part of pre-emptive multitasking. Eventually none of the tasks get any work done as the execution time per task becomes less and less as you add more tasks. Most of the tasks are asleep for most of the time. It is the same with BurnInTest. You can have near 100% hardware load with duty cycle settings in BurnInTest of less than 100%.

So if 100% duty cycle for all tests isn't the best, then what is? The best duty cycle setting to achieve 100% load your hardware depends on your hardware and your testing goals.
But typuical settings might be something like,
Disk 100% duty cycle
3D 100% duty cycle
RAM 80% duty cycle
CPU 80% duty cycle (as the RAM, disk and 3D tests also use the CPU, the actual CPU load might still be 100%, depending on your hardware)

Some example settings

What tests you select to run and the ideal duty cycle settings will vary depending on your testing requirements and the hardware in use. In most cases it is common sense. Some examples;

  • You want to test just your hard drive: Turn off all tests except the hard drive test and set the hard drive duty cycle to 100%
  • You want to test just your main RAM: Turn off all tests except the RAM test and set the hard drive duty cycle both to 100%
  • You want to generate maximum temperature: Different computers will have different (potentially) hot components. Typically these are the CPU and the video card. These generally use the most electrical power and thus generate the most heat. In this case set the CPU and GPGPU duty cycle to 100%. Also pick the Maximum Heat option in preferences for the CPU test.
  • You want to test the whole system: Turn on all applicable tests (those that correspond to the hardware in the machine). Then adjust the duty cycle settings until the CPU load is around 95% to 99%. Generally you still want to have the hard drive at 100% duty cycle however as it is the slowest component. We recommend around 99% rather than 100%+ as we want to keep sufficient CPU time available for the disk to run at maximum speed.
  • If the goal is to to maximise the GPU load we suggest the following. Select the DirectX 12 test in the preferences window (not the older DirectX 9 test). Maxmise the size of the window to fill the screen. Use a monitor with at least 4K resolution (or multiple 4K monitors for video cards that support it). Select both the GPGPU test and the 3D test to run at 100% duity cycle. Don't set the CPU test to 100%, becuase some CPU time is required for the 3D test.

Head back to the BurnInTest FAQ page.