Motorola MB7420

Overview
Certified by Comcast XFINITY, Charter Spectrum, Time Warner Cable, Cox, BrightHouse

MB7420 datasheet says that the core chipset is a Broadcom BCM33843D

16x4 DOCSIS 3.0 cable modem
 * 16 downstream channels for speeds up to 686 Mbps
 * 4 upstream channels for speeds up to 123 Mbps

Links of Interest
Datasheet