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New Modem - Slower Download Speed?

Regular Contributor

New Modem - Slower Download Speed?

I've been starting to have some issues with my Motorola SURFboard SB6141 so I went ahead and replaced it with a Motorola MB8600.


Running speed tests on the SURFboard were consistently in the 245 down / 23 up range.


Right before swapping out the modem it pulled 241.6 / 23.34.


However, a couple speed tests with the new modem are now pulling lower download numbers.  I've run three so far and the highest it's hit was 200.92 / 24.04 (other two were in the 170 range).


Why would a newer (and faster) modem be pulling lower download speeds than the old modem?


Re: New Modem - Slower Download Speed?

there could be a few reasons,


Which tier are you on.  try a factory reset on modem.  Im assuming its activated already.


I've noticed quite a bit of times when first setting up a new modem.  I have to have two separate Mac address's during initial setup.   When rebooting the modem.  I finally connect to my router.   Then I'd get full speed..  Initial setup 75% of the time had slower speeds if I left the same Mac address "computer" connected without factory reset.


Secondly the sb6141 had 8 channels on downstream. docsis 3.0

the mb8600 has 32 channels docsis 3.1


the 8600 give the opportunity to have a much more linear form of bandwidth limiting.


QAM factors.   8 6Mhz channels of 256-QAM will give you a maximum theoretical 343Mbps


in a docsis 3.1 modem QAM factor raises significantly 4096-QAM.   one channe 192Mhz can theoretically give you 1.89Gbps or 1890Mbps


if your modem is connecting on 3.1 currently and connected on 3.0 previously..   Comcast has now a greater and more efficient way of dialing back your speed to the provisioned rate subscribed.  


I am assuming your subscribed to "Extreme 150"???



Regular Contributor

Re: New Modem - Slower Download Speed?

Thanks for the reply.


I'll try resetting the modem and see what happens.


I looked at my bill and it says "Extreme Internet" and "Download as fast as 300 Mbps"


Re: New Modem - Slower Download Speed?

Just an FYI. If you do perform a factory reset to defaults, you will lose any customized settings, and they will need to be re-configured from scratch.

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