Surface book cpu frequence always on max after update to windows10 redstone(14393)

After updated my surface book to windows 10 redstone, I found my cpu frequence is always on max with no high cpu usage program run backgound.And under battery mode, cpu frequence stay on 2.47gzh(i5-6300u) and can not turbo to 2.9ghz, is anyone has the same issue?
Sorry for my poor English.

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