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64 of 79 people found the following review helpful
on June 16, 2009
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:
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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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15 of 16 people found the following review helpful
on August 5, 2009
The product works great. My downloads tested at 21 Mb/s and uploads at 4.54 Mb/s. I had thought that my router, a Linksys WRT55AG was the issue, especially since I had different speeds when directly connected to the older modem. Now the system flies with and without the router. I have Comcast and I believe that I am on the regular tier. The phone call to Comcast took a little longer (30 minutes) than other reviews, but I am completely satisfied with the new product.
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14 of 15 people found the following review helpful
on December 31, 2010
I scoured the internet for reviews and by far, the most recommended DOCSIS 3 modem for Comcast High Speed Internet is the Motorola SB6120. Why do you want DOCSIS 3? So you have a modem that works with the fastest speed plans available now and in the future.

I've had the modem for a couple weeks now and it's rock solid. The only issue I ran into was the modem shipped with an old firmware, SB6120-1.0.1.8-SCM02-NOSH, so I wasn't able to immediately connect. Motorola really needs to do a better job of supplying modems with up to date firmware. If you see the SEND and RECEIVE lights blinking together, that means a firmware update is in process. It takes a long time, just let it complete. It was taking so long I thought my internet connection was not working so I rebooted the modem but that only delayed things more, just let it finish! The fact SEND and RECEIVE are blinking means you are connected so let it finish updating. After the update, my firmare is SB612X-1.0.3.3-SCM00-NOSH.
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21 of 24 people found the following review helpful
on July 20, 2009
I read the reviews here and elsewhere and decided to try the combination of this Motorola SB6120 and the D-Link DIR 655. First, comparing the Motorola SB6120 with the Motorola SBG900 on Comcast. The highest speed I could get on the SBG900 was 14mb/s. Note that was on a 20mb/s subscription. The higher subscription is not valuable without a DOCSIS 3.0 modem, I learned. So I returned the SBG900, and got this combo. Now I'm getting an average of 21mb/s both with and without the D-Link DIR 655. The D-Link has slowed down my upload time by 0.2mb/s but that's it. Certainly not something I care about! This is an outstanding modem, even on the slowest Comcast speed. I've downgraded to my ISP's slowest speed now because the difference is too small for it to matter to me. Going from 16 to 20 subscription had me go from 21 to 23 in real speed tests with the Motorola SB6120 by itself. The modem was easy to set up and has been working great for four days now. I am very happy with this purchase.
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24 of 28 people found the following review helpful
on May 5, 2009
When we recently upgraded our southern MA Comcast service to the Ultra/Premium HS Internet, Comcast tech said we had to replace former self-owned Motorola docsis2.0 cable modem with this rental docsis3.0 model to handle the new bandwith and speed.

We have a gigabit router (d-link 655) directing traffic between two hard-wired desktops with gigabit NIC's and one wireless-G laptop.

Has worked flawlessly since March 25, 2009. File downloads really fly, even when downloading on multiple PC's at same time, but some busy web-sites still poke along (probably they are not yet upgraded to docsis3.0 on their end (or have bandwith limiters)- so we can only get data as fast as they are transmitting).
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17 of 19 people found the following review helpful
on August 20, 2011
I bought from Amazon (not a re-seller) a brand new Motorolla SB6120. However when I went to have Comcast install the modem, they said it was already on a customer's account. This makes them unable to let me use the modem. They could not do anything about it, so the only recourse was to return the modem to Amazon. I'm still going to use Amazon for my shopping, but my confidence that their "new" products are new has been unquestionably shaken.
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9 of 9 people found the following review helpful
on November 11, 2009
Upgraded from a ten year old DOCSIS 1 modem rented from Comcast. Installation was a breeze. Just bypassed my router and connected it directly to my computer. After powering up and preparing to call Comcast to give them the new MAC ID, I looked up at the screen and saw they'd already found the connection and offered to download their "new modem installation wizard." Got it and within a very few minutes the modem was fully operational.

Powered down to put my router (Linksys BEFSR41) back in line and upon powering up was fully back to normal with all connections active.

Ran speed tests before and after that showed downloads to be speedier by a factor of two to three and uploads up by a factor of about four. Now my bottlenecks are the router and network card. Will deal with those two issues soon, but am very pleased with the changes so far. The higher speed is readily apparent while browsing.

The only issue was in returning the rental modem. The Comcast agent said I had to call customer service to give them the MAC ID even though the modem was up and running due to having run the wizard. Went ahead and phoned them, but the new MAC ID was in their database as I'd expected, so there was no reason to have called.
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9 of 9 people found the following review helpful
on July 25, 2009
I ordered this modem to replace a dead SB4100 which I've been using for many years. Fully expecting a full-day installation project I was pleasantly surprised that the entire install took only a few minutes. A phone call to Cox Phoenix to register the modem and I was immediately enjoying blazingly fast downloads. Bonded channel indicator worked as advertised. Absolutely no problems after three days. I recommend this cable modem without reservation.
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8 of 8 people found the following review helpful
on January 11, 2011
I have been a customer of my cable provider - Comcast - for more than four years, and during of these years I rented RCA DCM425 modem. Honestly, I cannot say that this modem was total waste of my money, because it gave me promised speed of my plan; however, this modem crashed quite often, and I spent time to reboot this thing. This problem was not a big deal for me, but in the last two months, modem took whole day to reboot, and my download speed was five times smaller than it should be. I chose to buy my own modem, but anyone who think about buying own modem should consider these two factors.

First factor, the major benefit of having own modem is concluding in paying leasing fees that turned from reasonable two dollars per month into seven dollars per month in my area. The second is major drawback of having own modem is concluding that if anything happened with your own modem, it is going to be your responsibility to take care for this modem instead of Comcast.
After my decision is made, I checked the list of approved modems by my Internet provider on the official web site. This is important, because if Motorola SB6120 was not in the list, Comcast won't allow me to use this model of cable modem. Also, users must check end of life date in order to get permission from Comcast to use SB6120 or any other models.
Well, after some information about buying vs. leasing information, lets talk about the modem itself.

Inside The Box:
Pretty much everything that you should have for connection your new modem to your desktop or laptop.
10 of 10.

Design:
Well, design of this modem did not change my view of modems as devices with office austere style. We have black color which fits almost everyone and vertical position - it may place horizontal too - that make our modem looks as a solid choice for almost all users. I also like power adapter which is smaller and weighs less than RCA power adapter.
7 of 10.

Installation:
The process of installation is describing in the install sheet, but there are two steps that users must know. Disconnect leased modem and router. Then connect new modem directly to PC - remember that router must install only after modem is fully configured - . Remember, simple connection of all required cables and cord is not enough for Internet connection. In order to get Internet, users should select one of four possible ways to do this task. First, users can call Comcast to arrange modem installation if they feel that they cannot perform this task without professional help. On the other hand, full process of installation is really easy for most users. Just making a phone call to Comcast office after you connect the modem directly to computer, and tell them correct MAC address of your modem and some other stuff. All process will not take a lot of time. Third, users can use special CD from free Comcast installation kit. Just follow instructions, and you will be set in minutes; however, users must know that with Internet installation, they also installed several programs that they might not need at all like Norton(tm) Security Suite and Comcast version of Internet Explorer. Also, installation with CD might perform only one time, because if something went wrong and users exit the program, and then come back, they will see the error message - it may be something wrong with my installation CD - . The last step which I did in order to make things work is automatically pop-up Internet Explorer window with Comcast Self Activation Page. First enter your account number, then install required software and select replacing modem option from the list. The whole process will take some time - do not turn your PC off during installation - and then you will see the window with message that installation is completed and your account information. Considered that you do need to install drivers for this modem, and four ways to get Internet, the installation is so easy. The only drawback in my opinion is lack of USB connection that might be a big deal for some users.
10 of 10.

Performance:
The great thing which I say about modem is it does not get hot as my old one, because of well ventilated body of modem. The same compliment goes to power adapter which is also well designed. The other good thing about this modem is nice front panel lights that inform users about status of the modem. The negative things of this modem are lack of power and reset buttons. The only way to reset this modem is unplug the modem from the AC. The same goes to turn off the modem. This modem has never crashed - I own this modem for only two weeks - but I really prefer to have these buttons. The next and most important thing for any modems is download and upload speed. As was mentioned before, I did get promised speed by Comcast in the last two months - the best I got once was 12 Mbit/s download and 1.5 Mbit/s upload while the common speed was 3 Mbit/s download and 1 Mbit/s upload - My promised speeds by the provider are 15 Mbit/s downstream and 3 Mbit/s upstream. According to Speedtest.net, my download speed is 20 Mb/s and my upload speed is 3.5 Mb/s which match with Comcast PowerBoost. In addition, the version of DOCSIS is being a great factor in Mb/s race, and it strongly affects your Internet speed. In this case, this DOCSIS 3.0 modem has backwards compatible to DOCSSIS 2.0. Honestly, I have checked yet what version of DOCSIS is being used in my local Comcast area, but even if it is 2.0 it is great to have newest technology standard for future time.
8 of 10

Value:
In conclusion, I say that I like this modem very much. The installation is easy, the speed is great, ventilation system is very good, and newest DOCSSIS 3.0 is a great option. Of course, for some users who do not mind using modem with DOCSSIS 2.0, because their Internet providers will not update the network in present future, and users who want to buy modem with wireless router feature might save 10 bucks or pay more 20 bucks more for more featured modem, but in my case I think that 77.79 is a great price for this modem.
10 of 10.

The final grade is 9 of 10.
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8 of 8 people found the following review helpful
on February 21, 2011
Tired of paying the obscene Comcast modem rental fee ($7/month) I decided to buy my own modem. Before buying, I checked-out reviews for several DOCSIS 3.0 (the latest standard) cable modems. The Motorola SB6120 had good reviews, but apparently "some" Comcast users had trouble with this modem. To avoid problems, I called Comcast and asked if they supported the SB6120 modem? They said they did, and told me there shouldn't be any problem using the SB6120 on Comcast, as long as I notified them (tech support) after I installed the modem.

So, I ordered the Motorola SB6120 from Amazon, and it arrived in good condition in just a few days. The SB6120 comes with good simple instructions that would allow even the technically challenged to make the few necessary connections. After connecting-up the new Motorola modem I called Comcast tech support. They asked me for the MAC (Media Access Control) address, that was clearly listed on the modem. Then there was a brief initialization of the modem, by Comcast. After that I was ready to go, all in less than 10 minutes.

In summary, the Motorola SB6120 modem works fine for me on Comcast. In general, I've found Motorola products to be better than average. NOTE: make sure you get a receipt from Comcast that shows the serial number of the Comcast modem you returned. Even though I did this, I still had trouble getting them to stop charging me a rental fee for the modem; as well as various other problems from Comcast. If you aren't currently using Comcast, I suggest you keep it that way. However, for me, the Motorola SB6120 works great on Comcast. To date, no problems of any kind with the Motorola modem. If needed, I would buy another Motorola SB6120 modem.
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