We installed Xfinity 1000/40 residential service in, I think, 2017, and installed the SB8200 as the modem. It’s been working. (BIG thumbs up! I cannot complain about several years of flawless service.) 

When Xfinity bumped service to 1200 a couple years after that, we saw no immediate reason to change modem hardware. Just last week, tho, I discovered that they didn’t just bump it to 1200 down, they also bumped it to 200 up. Nobody talks about the uplink rate. I’ve only been seeing 40 up the whole time since. Well then! I would really like to bump up that uplink rate!

I called an Xfinity tech in, who tested the coax up to 2000/450, and what we’re paying for (1200/200), and then speed tested through the modem: the up link rate was 40 Mbps through the SB8200.

Is there something I can do to the SB8200 that’ll get me to the promised land (200 Mbps up)? If not, is there another Arris modem that fully supports Xfinity Docsis 3.1 1200/200 coax service?

I had just finished that sentence above when Josh from Xfinity called, since they text-asked whether the visit resolved the problem and I replied No. We talked about the tech visit and he mentioned that while the downlink rate was improved some time ago, uplink rate improvements are still happening as a rolling upgrade across our area, and that the bootfile they’re giving me for my SB8200 doesn’t configure it for the faster uplink rate. The uplink rate change has (seemingly) only started to happen as of a couple months ago. So my read of the upgrade situation as stated above appears to be w0rng, the uplink speed wasn’t upgraded with the downlink speed.

Long story short, The list of Xfinity recommended 3rd party modems that take advantage of higher supported uplink speeds atm are: Arris G54, NetGear CM3000 and CBR750, Hitron Coda and Coda56.