I want to upgrade my DOCSIS 2.0 Motorola sb5101u to a DOCSIS 3.0 model . I wonder how many Comcast customer know what internet speed they be pay for . I just spend 15 minute search within my account and I can not find any explicit mention of speed . however , my bill say I have get Preferred double Play and Comcast 's advertising say that come with speed of `` up to 20 mbp download speed with powerboost  '' . well , even with my old sb5101u , I be consistently get 23-25 mbp download and 3.6 mbp upload on my desktop connect to the router with a ethernet cable , so it be not surprising that the new modem do not give I any improvement . still , it work fine and I 'll keep it as a hedge against any improvement that be not obvious to I at the moment or thing that Comcast may have come down the pike . I do not try install the modem myself as I know Comcast would have to activate it from they end . it be not trivial for the Comcast agent at the other end of the phone . he keep mention something about get a IP address and not get a boot file . but , with a few retry and I unplug the modem and plug it back in to reset it , we be ultimately successful . what I take from my experience and the report of other be that the amount of agony one have to go through depend on the Comcast rep who get the call , BUT if you persevere the installation should ultimately prove successful .