Actually you should be able to control this behaviour via the performance settings. You can find it under settings>battery>battery saver and performance.
Can you check if it makes a difference for you? I haven't looked into it for a long time.
EDIT: In addition to the common (8974 platform) power settings there can also be further device specific settings. Like these. Maybe check what settings your m8 (which is also 8974 afaik) uses...