Bests & Worsts Reviews from Amazon

This Motorola MB7621 cable modem was a huge disappointment. I bought it to replace my four year old Arris SB6141 which is a 8x4 modem. The MB7621 is 24x8 so in theory it should give better performance. However, the performance I saw was much worse than the older SB6141 with download speeds. I have Comcast Performance Pro 150mb service and was routinely seeing about 100mb in real life with the old modem. When I put this new cable modem on the coax the download speed consistently dropped to about 32mb. The signal levels all looked good and there weren't any uncorrected codewords. It appeared that 23 of the 24 available download channels achieved a lock. After spending several hours playing around with settings, etc, and chatting with Comcast "support" (useless) I had to assume that it was somehow defective. Back to using my trusty old Arris SB6141, hopefully for a few more years. I noted another reviewer also saw speed slowdowns on this modem. Even though it is listed as being Comcast Xfinity compatible it certainly did not work for me.