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Which to Buy: the Arris Motorola SB6141 or SB6121?

What download speed can you expect from your DOCSIS 3.0 cable modem?

What download speed can you expect from your DOCSIS 3.0 cable modem?

A Modem Is "Must Have" Equipment in Many Homes

In most households, the modem is the way the devices access the Internet. Generally, you need a modem and a router to download and upload files, stream your movies to your devices, and play online games.

There are two main types of modems: DSL (Digital Subscriber Line) and cable. The cable modem is faster. It is also more popular, as approximately 90% of homes in the US are wired with coaxial cable for cable TV access.

Both the Arris Motorola SB6141 and the Arris Motorola SB6121 are cable modems. They have the two names “Arris” and “Motorola” because the Motorola division that manufactures these modems has been sold to the Arris Group, a manufacturer of high-speed data, video and telephony systems. They use the DOCSIS 3.0 standard to move data over cable networks.

DOCSIS 3.0 Explained

DOCSIS stands for Data Over Cable Service Interface Specification, an international standard for data transfer over cable TV (CATV) systems. Internet service providers use it to provide internet access using existing hybrid fiber-coaxial (HFC) infrastructure.

CableLabs led a consortium of thirteen networking and electronics companies that jointly developed the DOCSIS standard.

The first version of DOCSIS, Version 1.0, was published in March 1997 while the latest version, DOCSIS 3.0, was published in August 2006, to meet increasing demands for symmetric services such as IP telephony.

DOCSIS 3.0 is a very practical standard as it maintains cross-version compatibility; devices using older versions can communicate with newer devices using the highest supported version common to both devices.

Channel Bonding

The data pipes are similar to water pipes. The diameter of the pipe determines the quantity that can flow through.

The data pipes are similar to water pipes. The diameter of the pipe determines the quantity that can flow through.

The DOCSIS 3.0 standard enables cable Internet providers to exploit extra capacity through channel-bonding technology.

So what is channel bonding and how does it work in the Motorola SB6141 or SB6121?

It’s All About Size

Bigger pipe allows more to go through at the same time = speed increase

Bigger pipe allows more to go through at the same time = speed increase

Channel bonding, instead of using individual smaller pipes to transmit data in parallel, combines smaller data pipes are combined into one large single broadband conduit.

The Motorola SB6141, instead of having eight single pipes or channels with each transmitting at a maximum of 40 Mbps, uses channel bonding to combine all eight channels into a single huge channel with a theoretical maximum output of 320 Mbps.

The older Motorola SB6121 combines four channels to give you a maximum theoretical output of 160 Mbps.

Upstream, both the Motorola SB6141 and SB6121 bond four upstream channels to give you over 100 Mbps when sending or uploading data.

Essentially, the Motorola SB6141 is theoretically twice as fast downstream as the Motorola SB6121, and both give service providers the ability to provide multimedia and telephony to their customers.

Wow, Can I Really Have 320 Mbps of Throughput with the Motorola SB6141?

320 Mbps of throughput? Wow, that would be truly excellent. But, unfortunately, that is only the theoretical speed. In the real world, the actual speed will always be less.

Transmission speeds are always approximate: they depend on different factors such as the network configuration, the capacity of the network, the volume of traffic on the network, and geographic location. Also, overhead factors such as error correction coding (ECC), burst preamble, and guard interval reduce speed below the theoretical maximum.

What Is the Fastest Speed That I Can Expect?

In recent years, providers have announced huge increases in speed. In 2010, the U.S. Federal Communications Commission (FCC) encouraged U.S. providers to make 100 Mbps available to approximately 100 million households before 2020. In 2010, Videotron announced 120 Mbps download and 20 Mbps upload service in Quebec City. In 2011, Shaw Cable announced it would provide 250 Mbps download and 15Mbps upload for its customers, and in the United Kingdom, Virgin Media said it would start trials of a whopping download speed of 1.5 Gbps and upload speed of 150 Mbps.

Few wired technologies can handle these speeds; so far, only DOCSIS, FIOS, E-line (an advanced Powerline type of network with a bandwidth equivalent to fiber) and Ethernet.

So, can these two modems take advantage of these developments? Certainly, even with transmission losses, DOCSIS 3.0 modems can handle very high speeds. However, in the real world where money talks, you get only the speed that you can pay for. The top speed is limited by the package you buy from the various providers, such as Comcast/Xfinity, TWC (Time-Warner Cable), Cox, Charter, Mediacom, and others.

In general, in daily use, you will typically get a download speed of between 30 to 40 Mbps from a Motorola SB6141 DOCSIS 3.0 cable modem, which is very fast by today's standards.

Should You Choose the Motorola SB6141 Over the SB6121?

At the end of the day, the choice is yours. The two modems are equally good and look identical; it’s just that the Motorola SB6141 is twice as fast as the Motorola SB6121, on the download side.

Now, if you were a Shaw Cable subscriber in an area where that company was providing 250 Mbps throughput, or if you were in the UK and subscribing to Virgin Media, you would ABSOLUTELY want to get the Motorola SB6141 to be able to enjoy the maximum capacity. Or if you had some other provider providing speeds approaching 100 Mbps—providers are changing and upgrading all the time—you would want the faster modem.

It's Up to You

But clearly, for most people, the Motorola SB6121 is more than sufficient for now.

Then again, many hope to take advantage of the capabilities of the SB6141 in the future. They get newer and faster hardware for a small difference in price, and if their service provider makes more bandwidth available, they won’t have to replace their modem.

By the way, just a tip for you; due to aggressive pricing at Amazon, sometimes you will find that the Motorola SB6141 is even cheaper than the Motorola SB6121. Keep checking prices there.

A quick snapshot of the Motorola SB6121 vs SB6141

A quick snapshot of the Motorola SB6121 vs SB6141

What you can get with the Arris Motorola SB6141

What you do not get:

  • It does not provide a Router function. As such you cannot get Wifi with just the Motorola SB6141. You will need to connect a wireless router to it to get WiFi. The other option is to get a cable modem router combo in one box which the latest Arris Motorola offering, the Arris Motorola SBG6700AC gateway.
  • You cannot connect your telephone to it as it does not have a telephone jack. If you need a cable modem with a telephone jack, check out the Arris TM822G
  • It has only 1 Ethernet port. If you need a VOIP function, you will also need to add a router.
  • It cannot work with Verizon FiOS or AT&T U-verse

Now that you know what you do not have with the SB6141, here are features that you can enjoy from the Motorola SB6141:

  • Cable only modem that is compatible with Comcast/Xfinity, Cox, Charter, Time Warner, Mediacom and Bright House. If you are not sure, call your service provider to vaildate
  • Lightning-fast broadband speed with download data rates of up to 343 Mbps and upload rate of up to 131 Mbps; note that the speeds are dependent upon your Cable Internet provider service and those two speed rates are the theoretical rates
  • Works with Windows, Macintosh, and UNIX computers
  • IPv4 and IPv6 supported

or you can get the Motorola SB6121 with the same pros and cons of the SB6141 but at half the speed of the Motorola SB6141.

If you prefer the very newest and fastest, then you should check out the Motorola SB6183 introduced in 2014. It is two times faster than the Motorola SB6141!

Update - Aug 2016

I know some of us really like the latest. After the Motorola SB6183, Arris released the Arris Motorola SB6190. Check out the following link if you like to look at a comparison between the Arris Motorola SB6180 and SB6193.

Don't Let Your Router Slow You Down

If you have just decided to buy either the Motorola SB6141 or SB6121, and if you are using Windows and accessing the internet via a wireless router—especially an AC class wireless router—then you should look into investing in a speedy wireless client card, to make full use of the speed of your modem.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2013 James Causian

We would love to hear your comments...

Angkor79 on August 23, 2017:

It's a straight lie. SB6141 is not capable of 343Mbps not even 250Mbps. Yes, it will do up to 70 or 80Mbps. If you're buying this modem to future proof just in case someday you will upgrade your internet to faster speed using this same modem, don't do it. You will be disappointed becuz it will never get anywhere closed to 100Mbps. Fucking false advertisement, up to 343Mbps download speed my ass! Just got confirmed from Comcast that SB6141 can't deliver the speed as they said on the box

Bob on July 03, 2015:

"Now, if you were a Shaw Cable subscriber in an area where that company was providing 250 Mbps throughput, or if you were in the UK and subscribing to Virgin Media, you would ABSOLUTELY want to get the Motorola SB6141 to be able to enjoy the maximum capacity."

What's the use case for this? What would a person download today that can use that kind of bandwidth?

10 simultaneous streams of 4K video?

I guess maybe software downloads, but even downloading 100 MB, the difference in time is just a few seconds, and the bottleneck is probably not the last mile, anyway.

Except for pirating movies, it's going to be a long time before we have anything consumer-facing that can seriously saturate a 250 Mbps line.

James Causian (author) from Huston, Texas on May 15, 2015:

That makes either of the SB6121 or SB6141 "cheap" in relation to the service cost doesn't it? As such, on a personal preference, I wouldn't mind spending a few dollars more for the newer Motorola SB6141 or even the SB6183 hardware. You can check out my other hub to see if the the Motorola SB6183 is for you or not via this link - before you make any decision.

Gpac on May 12, 2015:

Basic comcast internet is 25MB next level is 50MB. You have to pay over $100 on internet alone to get anything iver $100mB

James Causian (author) from Huston, Texas on March 28, 2015:

Thank you aveygr. I am glad that the hub was useful to you. Please share it so that it can benefit others as well.

aveygr on March 28, 2015:

Very, very well written and easy to absorb article. "Thank You" for doing

the article in such simplistic terms that those without knowledge of bandwidth can grasp it and feel educated.

James Causian (author) from Huston, Texas on May 16, 2014:

You are welcome. Glad that the info has been helpful to you.

Danny on May 16, 2014:

Thank you so much. That was so informative for someone who had no idea of DOCSIS and channel bonding like me. Made my choice easier.

redsam on March 09, 2014:

Although the article explains how one modem combines 8 channels into one and the other does only 4 into 1, it did not explain why there were 'channels' to begin with.

el on March 08, 2014:

Thanks for the explanation in simple terms which a non technical person can understand. For the first time I clearly understood the why difference between the 2.

Mindful Marketing Strategies on February 09, 2014:

Thanks for the comparison between the two modems. I should have done this a while back and just purchased my cable modem instead of leasing it from my cable provider for the past 2 years. Looks like for a simple home network the SB6121 will suffice.