Cable Modem Buying Guide

The following cable modem buying guide will help you decide which modem you should choose as your network device. Learn about various factors like ISP (internet service provider) compatibility, modem channel bonding, and the modems to avoid when selecting the correct cable modem for you.

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Choosing the Right Cable Modem in 3 Steps

Step 1: ISP Compatibility

First of all, you should consider ISP compatibility. When choosing the right cable modem, make sure your ISP has approved the modem for use on their network. Many people think any modem will work with their service provider. In most cases, this is not true, so use a certified modem (links to ISP approved modems listed below).


Astound Broadband powered by Grande

Astound Broadband powered by RCN

Astound Broadband powered by Wave

Blue Ridge


Charter Spectrum










Step 2: Speed Factor

Consider your internet speed. If your internet plan produces a 300 Mbps speed, an 8×4 channel modem (with a max theoretical speed of 343 Mbps or about 215 Mbps in actual speed) would not get you your full speed you are paying for with your ISP. However, a 16×4 channel modem (max theoretical speed of 686 Mbps or about 372 Mbps in actual speed) would allow you to achieve your full speed.

Keep in mind, some internet service providers will increase your speed for free for various reasons. DOCSIS 3.0 modems will eventually become end-of-life, so it is strongly recommended to purchase a DOCSIS 3.1 modem. Some ISPs have already moved to exclusive use of DOCSIS 3.1 devices.

Even if your modem is capable of a faster speed than your current internet plan (e.g. a DOCSIS 3.1 modem), future-proofing benefits you in time. Read more below about advertised modem speeds.

Step 3: Avoid Intel Puma Chipset Modems

Many cable modems include Intel Puma 6 chipsets that have known issues with network latency and network jitter. You may read more about the issues on the Intel Puma 6 chipset defects page, which also contains the full bad modems list (the do not buy list). To indicate a bad modem, will mark an Intel Puma chipset modem with a ♦ symbol.

Things You Should Know About Cable Modems

Why Buy Your Own Cable Modem?

The first reason to purchase your own modem is to save money. ISPs may charge up to $15 a month to rent one of their old modems. Therefore, you can save up to $180 a year on rental fees. Of course, those rental fees will continue to increase every year as well.

After five years, you could save up to $900!

The second reason for buying your own device allows you to pick which features you want in your modem, as opposed to the ISP forcing a limited features modem on you. Therefore, you have control over the brand and specifications of the modem.

Inaccurate Advertised Speed Claims

Even though cable modem manufacturers state a certain speed on their modem packages, those speeds are usually unobtainable. For example, the NETGEAR CM400 modem states a speed on the package up to 340 Mbps. However, ISPs will limit this speed for various reasons. Comcast states the CM400 will actually reach speeds up to 215 Mbps on their network.

The speed you get will only be a certain percentage of the stated package specification. Why is that? Various factors like the type of server, total number of users on the network, computer equipment, services offered by the internet provider, and other factors will throttle the full output of your modem speed.

Keep in mind that the stated data rate (download and upload speed) is just a maximum theoretical number.

Even DOCSIS 3.1 modems may advertise speeds of 6 or 10 Gbps, however the ISPs will limit these cable modems to 2.5 Gbps or slower due to network capabilities.

Cable Modem Channel Bonding

When you see a modem with 16×4 channel bonding, that means it has 16 channels for downloading and 4 channels for uploading.

The rule is simple – the more channels a modem has, the faster the data rates will be. So, a 16×4 channel modem achieves a faster data rate than an 8×4 channel modem.

In other words, the more data channels your modem has, the more speed the ISP can push to your home (if you have purchased the fastest speed tier from your ISP).

The chart below explains the speeds for each channel tier.

Channels (DOCSIS 3.0)Max Theoretical Speed
4×4172 Mbps
8×4343 Mbps
16×4686 Mbps
24×81 Gbps or 1000 Mbps
32×81.4 Gbps or 1400 Mbps
32×8 (DOCSIS 3.0 mode)
10 Gbps or 10,000 Mbps

ISPs use the data channels of the modem to deliver the internet to your home. The internet is like a highway and bottlenecks and slows during peak hours. However, having more lanes of traffic or data channels allows you to avoid congestion and keeps your full download speeds going.

DOCSIS 3.0 vs. DOCSIS 3.1

Data Over Cable Service Interface Specification (DOCSIS) allows for the transporting of data over a coaxial cable (internet service).

The most widely used format by cable internet providers remains DOCSIS 3.0. Most ISPs support DOCSIS 3.1, although some neighborhoods may have to wait years before DOCSIS 3.1 capability reaches them.

The main difference between DOCSIS 3.0 and 3.1 is the capable speeds. Comcast states that a DOCSIS 3.0 32×8 channel modem will reach actual speeds of about 935 Mbps on their network. While a DOCSIS 3.1 modem will achieve a speed of 1000 Mbps or 1 Gbps or faster. If you want speeds in excess of 1 Gbps (for future-proofing), you need a DOCSIS 3.1 modem.

DOCSIS 3.1 features backwards compatibility with a DOCSIS 3.0 network. So, if your ISP has not yet upgraded to DOCSIS 3.1, a DOCSIS 3.1 modem will still function on a DOCSIS 3.0 network.

Pros and Cons of Combo Modem and Router Devices

Many network devices classify as combo units. In other words, a cable modem and a WiFi router combined into one device. The list below contains the pros and cons of these devices.


  • Less clutter (one less power cable and one less device)
  • Less hassle to set up since there is only one device


  • If either the router or modem fails or becomes obsolete, you have to replace the entire device
  • Locked into the capabilities of a most likely limited WiFi router, as opposed to buying a separate, better WiFi router with more advanced features

Consequently, it is usually cheaper and easier to upgrade modems and routers separately.

Cable Modems vs. DSL Modems

DSL technology is older and slower. Most DSL providers are not in a hurry to upgrade their phone lines. If you have a choice of internet service providers, choose a cable internet company.  A few cable modems are capable of reaching speeds beyond 1000 Mbps (or 1 Gbps). DSL cannot compete with the ultra fast speeds of cable internet (or fiber internet).

Cable Modem Care

Modems require little care. The most important thing to remember is that cable modems can get really warm. Do not block the vents on the cable modem. Also, make sure you have enough ventilation circulating around the device.

Finally, do not leave modems near heat sources. Your modem should function properly without any other maintenance (other than occasionally dusting the device).

Cable modems come from several manufacturers, but the most popular ones are ARRIS, NETGEAR, and Motorola. If you are looking for a company to support your device for the next several years, those mentioned earlier are your best bets.

Warranties will range from one-year to two-years from the modem manufacturers. Cable modems rarely fail as long as they do not get too hot. Also, if you buy a new modem from Amazon, they will offer an inexpensive extended warranty (just a few dollars to add three or four-year coverage).

Brand New vs. Used Modems

Avoid purchasing a used modem. A pre-owned modem may not have been deactivated from the previous owner’s account, which will likely leave you with a worthless device. Plus, with a used modem, you have no idea of the condition of the equipment. The previous owners’ may have immersed it in liquids or encountered some other disastrous event with the modem; it could be a fire hazard! Always buy a new modem to avoid hassles.


To help you decide which cable modem to choose, please follow the three steps at the top of this page.

To summarize:

  1. ISP Compatibility
  2. Speed Factors
  3. Avoid Intel Puma Chipset Modems

With the many options for modems, reviewing your ISP approved modems page may help with deciding which modem is right for you. The best DOCSIS 3.1 cable modem today belongs to the Motorola MB8600, which most major ISPs support.

Motorola MB8600 DOCSIS 3.1 Cable Approved Modems
Motorola MB8600 DOCSIS 3.1 Cable Modem


Motorola MB8600 INFO