@ssb1551 I was trying to find the answer but couldn't. The AMD site has not mentioned supported speed on their website. However, on Gigabyte's site for supported mobo's, they have mentioned that after 2667MHz, speed may vary depending upon CPU. So I guess 2667MHz is the maximum possible speed on stock (without overclock).
Is your system up and running? If yes, you can check and let us know the speed. It is very easy to find via command box.
type "wmic memorychip get speed" in cmd. you'll get the actual MHz of all RAM sticks installed in the system.
screenshot of my official laptop:
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