computer goes to powersaving mode when playing

Let's look at the situation that EA / DICE is in.

They live in a house infested with termites (get it? BUGS!). They know that the house is full of termites and it is not safe to live in the house, but they can not afford to tear down the whole house all at once and rebuild. They are fixing one support beam, and cross members at a time until they can fix the whole house.

Another word, EA / DICE know they have issues with this game and are fixing one item at a time based on the priority of what they deem important.

I am assuming that this may be one of their lower priority issues as you are stil lable to play the game, just in Power Saving mode. I know you said you turned off all power saving modes, but did this happen when you were on battery or on ac? Sometimes, company like dell have their own battery monitor pre-installed from the factory and you may want to check the setting on that too.

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Maybe your graphics card can't do the job and crashes ?  what are your pc specs?