Customer Review

64 of 79 people found the following review helpful
5.0 out of 5 stars Very Fast Modem, make sure to update your routers firmware though, June 15, 2009
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This review is from: Motorola SB6120 SURFboard DOCSIS 3.0 eXtreme Broadband Cable Modem (Personal Computers)
When Comcast upgraded South Florida to DOCSIS 3.0 I decided to upgrade from a SB5100 to this for my home network. The initial installation went by okay, it takes about 5 min to find a signal from Comcast (alot slower then the older 5xxx series surfboards) but when it finally connected I ran a speedtest and it was connecting at 32,000/4,000 which was amazing because I was only paying for 12,000/2,000 service.

The only trouble that I experienced with this modem was when I tried to hook it up to my D-Link DIR-655, upon my first attempt it would not establish a connection at all using the 1.11 firmware that I was using with my router. So I tried to see if it would work with newer firmware, I went to the D-Link website and downloaded the latest firmware on their website at the time which was version 1.21. That firmware allowed the router to establish a connection with my SB6120 but the signal would drop any time that one of the computers with a wireless adapter would try to download anything or stream stuff. My frustration made me think about using google to find an answer to my problem so I eventually found a link to d-links ftp server on a forum where they had their unreleased beta firmware. I installed the beta firmware 1.32NA which was the latest they had on June 15, 2009. The beta firmware has made the connection more stable and I havent had any problems since upgrading my firmware (review updated on April 3, 2010).

If you have connection issues or poor signal strength:
If you are having issues with your signal strength I would also recommend trying to remove any amplifiers you might be using on your cable tv to see if it fixes your connection drops. I was experiencing issues with connection drops that turned out to be a bad generic amplifier that comcast gave me, once it was removed the connection drops stopped but the signal strength wasnt very good (-3 db signal strength without an amp & I was running the line directly from the outside to the modem) so I purchased a different amplifier later on that greatly improved my signal strength to +7db - +9db.

I would highly recommend removing any excessive couplings, splitters, or objects you have to extend/join your RG6 cables because they interfere with your signal and water it down to the point where you get almost no signal when it gets to its destination. If you are in the market for an amplifier that will work with your modem I suggest using either a 4 PORT CABLE TV / HDTV / DIGITAL AMPLIFIER INTERNET MODEM SIGNAL BOOSTER INTERNET AMP or a 8-Port Bi-Directional Cable TV HDTV Amplifier Splitter Signal Booster with Passive Return Path where the line comes in from the outside to all the connections in your house, you will see a huge improvement in signal strength.

If you need to check the signal strength of your modem go to ip adress [...] and look for the tab on the top that says "signal" you will be able to see the signal to noise ratio and power level information in this area.
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Tracked by 6 customers

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Showing 1-10 of 20 posts in this discussion
Initial post: Jul 15, 2009 10:07:14 AM PDT
atonaldenim says:
Comcast can be picky about what MAC address is connected to the cable modem... if you originally set it up directly connected to your computer, Comcast will often remember this MAC address and only connect to this MAC. Often when using a router you need to configure it to clone the MAC address of the computer the internet was originally set up on.

Not sure if this is relevant to your situation, but it's worth mentioning.

Posted on Aug 25, 2009 8:50:41 AM PDT
FunShop says:
I bought this cable modem and it has worked very well with my DIR-655 router. I'm not sure if you have upgraded the router to one of the latest firmware versions. I'm still on version 1.20 and it works well.

Posted on Sep 24, 2009 7:31:42 AM PDT
Aakash Sahai says:
Perhaps it is your D-Link router (or the firmware) that can't handle the increased burst speeds you get with this modem.

In reply to an earlier post on Sep 26, 2009 2:14:40 PM PDT
Last edited by the author on Sep 26, 2009 2:16:04 PM PDT
I agree - I believe the problem I had with a Motorola SB5101 modem (frequently and persistently losing my Internet connection) was due to adding the D-Link DIR-825 router - when I take the router out of the picture, I never lose my Internet connection. D-Link Tech Support was no help. I've ordered the Motorola SB6120 in full confidence that I'll get an even faster connection speed, then I'll find a router that's proven to work with it.

Posted on Sep 27, 2009 11:22:19 AM PDT
C. Hallowell says:
I have a Motorola SB6120 DOCSIS 3 modem connected to a D-Link DIR-655 XtremeN Wireless Gigabit Router that feeds a D-Link DWA-552 XtremeN Wireless Desktop PCI Adapter that's 30 feet away, with an 8-inch-thick cinderblock wall, large kitchen appliances, a plaster wall, and a steel filing cabinet between the router and the wireless adapter.
Download speeds measured at the "main" computer (DELL 3100, 3.06 P4, 2 GB RAM @ 533Mhz.)= 32,500 kbps download; 6,000 kbps upload (COX Cable, WITHOUT paying extra for their "DOCSIS 3" service).
Satellite computer (DELL XPS600, 600Mhz. P3, 768 Mhz. RAM @133 Mhz.) with DWA-552 Adapter installed, recieves at about half of the speed that's coming off the modem = 14,400 kbps download, 3,300 kbps upload.
I attribute a lot of the difference in speeds to the old age and lower processor capacity of the satellite computer.
The SB6120 is FAR above any and all of the old DOCSIS 2 modems -- the new DOCSIS 3 technology makes the SB6120 an absolute MUST for gamers !!!
Dropped connections !!!???? Never had that problem AT ALL -- The trick is to set up the router properly and get it synced in with the proper wireless adapter.
One other thing --- BOTH of my computers have an Intel 1000 GT Pro 10/100/1000 Eternet card installed -- because the whole deal is only as good as your Ethernet card !!!

Posted on Oct 5, 2009 5:21:39 PM PDT
ArizonaOnly says:
I am having the same issue. DIR-655 worked fine with my older modem, and is otherwise working fine. And the SB6120 works fine when connected directly to my computer. But when I hook the router to the modem, no dice. It won't connect. Any suggestions. I have Cox service.

In reply to an earlier post on Oct 6, 2009 9:07:08 AM PDT
C. Hallowell says:
I'm located in Phoenix, and have COX Cable -- with the "next-to-highest" service tier.
In order to get your SB6120 to work properly with the D-Link DIR-655, you MUST enter the "Setup" mode for the Router's software -- find the "Clone Your Computer's MAC Adress" box -- and be sure that your Computer's MAC Addy is the "operative" one.
The modem is originally activated by COX when they enter the MAC Addy that is on the bottom of your SB6120 MODEM.
The DIR-655's set-up software let's you clone the MAC Addy into the Router -- and you will also need to synchronize your Router settings with your Wireless Adapter settings.
Take your time, and check all settings carefully -- The combibation of an SB6120 DOCSIS 3 Modem, D-Link Dir-655 Router, and the D-Link DWA-552 ExtremeN Wireless Adapter has served my needs very well -- and I have a plenty of speed, with ZERO dropped connections.
Internet connection speed, latency, and packet-loss tests taken at different times of the day indicate that this combination provides and maintains fast, consistant, and secure internet connections.

In reply to an earlier post on Oct 6, 2009 12:11:01 PM PDT
ArizonaOnly says:
Once you set the router MAC address to that of the computer that was connected when Cox activates it works! And this baby is FAST!!! I am getting 35 Mb/s download speeds. Amazing!

In reply to an earlier post on Oct 6, 2009 1:23:09 PM PDT
C. Hallowell says:
Not only is the SB6120 very FAST, but the DOCSIS 3 technology PROTECTS those high speeds against the automatic slow-down that comes with high-traffic-flow of the daytime hours.
Thousands of speed tests taken with the old DOCSIS 2 modem showed a DRASTIC drop-off of connection speeds during daily business/school hours -- which the new DOCSIS 3 SB6120 has eliminated completely !!
For example: The old SB5120 gave speeds of 22Mbps (down) and 2.6 Mbps (up) when measured at 6:00 AM, but those speeds would drop to 12-14 Mbps (down) and 1.2-1.8 Mbps when measured at 6:00 PM.
The new SB6120 gives 28-30 Mbps (down) and 3.5-6.0 Mbps (up) at ANY TIME during the day or night.

Posted on Oct 22, 2009 7:29:23 PM PDT
Last edited by the author on Oct 22, 2009 7:29:51 PM PDT
D-Link or Linksys router don't usually have great firmware. If you do want to have a stable router with good performance, pick a router which is supported by DD-WRT. The problem is not the modem, it's the router.
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