I replace the modem I be rent from Comcast with the Motorola sb6121 a few week ago and it have work very well since . activation with the cable company take about 10 minute which be longer than the technician expect but this could have be due to the quality of my connection as much as it could have be due to the modem . I have have no problem since . the technician I work with say that this be the same model modem he have and that it be a good selection . I have not notice significantly faster , or slower , datum rate since install .