That's 200MHz higher than the chip AMD showed at last month's New Horizon event.
You can see those clocks at the below screenshot, where "1D3601A2M88F3_39/36_N" (the code for the engineering sample Ryzen chip) makes it clear this is an F3 stepping processor, with the 39 referring to the boost clock, and the 36 referring to its base clock.
According to the rumor mill, AMD already has F4 stepping chips running at a boost clock of 4GHz.
Source: Hardwareluxx