3 Messages

Wed, Dec 1, 2021 4:48 AM


Slow speed

I also have the same issue, with the exception that I upgraded to the 900 Mbps plan (from my existing 200 Mbps plan), as the datasheet for my MB7621 modem said it was good for a data rate up to 1,029 Mbps, and the modem itself is described as the '24x8 960 Mbps Cable Modem, Model MB7621'.

Using CAT6 cable hardwired from my MacBook Pro to my router, I'm only getting speeds of around 187 Mbps down using Xfinity's Speed Test tool.

My Motorola MB7621 modem boot configuration file is 'd11_m_mb7621_ultrafast_c01.cm'.

Thanks in advance for any assistance.

This post was created from this comment on different post

Accepted Solution




93.7K Messages

Hace 6 m

It doesn't matter what speed the manufacturer rates it for. Only the speed that Comcast rates it for matters. They rate it for up to 845 Mbps: https://www.xfinity.com/support/devices#details 

What happens is that when you use an incompatible modem for a faster speed tier, the modem will default to using an even slower configuration file, so you will get even slower speeds than before. You need to use a compatible device. You can search for one at that link that I supplied.


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