I have be use my own Motorola sb4200 with Comcast for quite a while . so long , that Comcast inform I that the unit be now `` end of support '' , and that I might be get less throughput than I be pay for , due to the old hardware . purchase the sb6121 , and spend a couple of minute on the phone with Comcast support to get the new modem activate . speed test on the old sb4200 just before I unplug it : 12mb down \/ 2mb up . speed test on the new sb6121 -lrb- same website , minute apart -rrb- : 24.5 mb down \/ 3.6 mb up . I be so stunned by the improvement that I ask Comcast support to confirm that they have provision it for the proper rate on my account . the answer come back `` affirmative . '' the novelty of rapid download have not wear off yet - android update to my Touchpad report `` 19 % , 65 % , do ! '' , and that be over wi-fus ! as the title indicate , color I thrill !