Quad Exynos seems to perform impressively in browser and GPU bench. But Krait S4 is following closely.
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For Exynos/LTE combo to happen, samsung has to develop their own LTE chip or pair it with new Qualcomm LTE radio (MDM9615?) that supports non-snapdragon AP. I guess they are already working in that direction, but could have decided on Krait S4 due to timing to US market.