I recently bought a new Surface Pro 4. I run on battery often and configure the display’s brightness to 25% (with adaptive brightness disabled) to conserve battery.
With adaptive brightness disabled, my display would still occasionally darken or lighten unexpectedly, often to an uncomfortable level. After some experimentation, the trigger turned out to be what was visible on the screen. Darker content resulted in the display darkening, and lighter content resulted in the display brightening.
After some research, the culprit turned out to be Intel Display Power Saving Technology or DPST. The design of this Intel feature is precisely what I experienced: to save power by adjusting the display brightness depending on how dark or light the content on screen is.
While well intentioned, I found the experience incredibly disruptive given its slow and choppy transition and the uncomfortably dark end result. With my display brightness configured to 25% already, you can imagine how any darker might be uncomfortable, especially in adverse lighting conditions.
While on older desktops you could disable DPST via Intel’s driver configuration software, this software isn’t available on the Surface line with the recommended graphics drivers. While some might have success installing the latest available drivers and software from Intel directly, the steps can be complicated to replace the recommended drivers, and you risk introducing more problems with an untested configuration. My options seemed limited to living with it.
Fortunately, via work channels, I discovered an obscure registry key that can enable or disable Intel graphics features with the recommended graphics drivers.
The FeatureTestControl registry key is a bit field where each bit represents a feature. A value of 0 indicates the feature is enabled, and a value of 1 indicates the feature is disabled. The Intel graphics driver reads this registry key on initialization to determine which features to enable. The bit corresponding to DPST is the fifth bit from the right.
To disable DPST, you’ll need to set the DPST bit to 1. If the value of the registry key is 9240 as shown above, simply replace it with 9250. If the value on your system differs and you are unsure if DPST is already disabled, enter the existing hex value into Calculator’s Programmer mode (select HEX before entering the number) and switch to its bit toggling keypad to check the value of the DPST bit (position 4). If it is already set to 1, then DPST is already disabled. If not, click the bit to toggle it to 1, then copy the updated hex value into the registry. If updated correctly, the only number that should be different is the 4 (or whatever number was in that position), and it should be odd (or b, d, or f for the hex representation of 11, 13, or 15).
Reboot to ensure the graphics driver reconfigures itself, and DPST will be disabled.
Note: OS updates appear to reset the FeatureTestControl registry key back to its default value. If you notice that DPST has been reenabled, you’ve likely taken an OS update and will need to reconfigure the value in the registry again. Also, the registry key may be under […\0001] rather than […\0000] depending on the system and OS version installed.