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).

Atlantic Broadband
Blue Ridge
Cable ONE
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.

Even if your modem produces a faster speed than your internet plan (e.g. a DOCSIS 3.1 modem), future-proofing benefits you sooner or later. Read more below about advertised modem speeds.

Step 3: Avoid Intel Puma Chipset Modems

Many cable modems have 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 $12 a month to rent one of their old modems. Therefore, you can save up to $144 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 $720! Consequently, you can buy a modem for as low as $40 and use it for years.

Reason #2 for buying your own device: you can 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, color, and specifications of the modem.

Inaccurate Advertised Speed Claims

Even though cable modem manufacturers state a certain speed on their boxes, those speeds are 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 1 Gbps 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 setting.

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 3.1)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 many 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 650 to 700 Mbps on their network. While a DOCSIS 3.1 32×8 channel modem will achieve a speed of 1000 Mbps or 1 Gbps. You will see at least a 30% speed boost over the older technology, if the ISP offers gigabit internet.

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 select few cable modems are capable of reaching speeds of 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).

Popular Brands

Cable modems come from several manufacturers, but the most popular ones are ARRIS, NETGEAR, TP-Link, Motorola, and Linksys. 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. You will know in the first few hours of operation if your modem works. 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 (usually about $2 to add three or four-year coverage).


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 value cable modem today belongs to the NETGEAR CM500, which most major ISPs support.

NETGEAR CM500 DOCSIS 3.0 Cable Approved Modems
NETGEAR CM500 Cable Modem



14 thoughts on “Cable Modem Buying Guide”

  1. I am about to buy internet modem. What is the best wireless router? Docsis3.1 and channels 32down?
    That works with your RCN..
    Can you give me a list of companies and models so I can buy.

    Thanks a lot

  2. I want to hookup my own internet phone service (Huma). I have not seen modems listed that allow this except for Xfinity. Can you shed any light on this subject?

    • Did a Google search for Huma phone service – nothing popped up.

      Maybe you meant Ooma, which requires an Ooma device and a router (any will work), a modem, and an internet service provider (ISP). Ooma only provides phone service; they are not an internet service provider.

      So, for a normal setup, if you already have an ISP and a modem, you just need to add a router (which you may already own). Once you have any router, connect that to the Ooma device. You do not need a special modem or router for Ooma service.

      If you meant Ooma, here are some instructions to help setup the devices.

  3. I currently rent from xfinity My bill reads ” Internet/voice equipment rental ” if that tell u what I want to replace? the rental is 14.00 per month.What should I buy to replace it? Thanks. Jack

    • Hello John,

      Check out the XFINITY Approved Modems page. There are recommended modems depending on if you just need a cheap modem or WiFi or if you are going for the fastest speed available in your area (DOCSIS 3.1 modems). At the time of wiritng this, the NETGEAR CM400 on Amazon is only $30! That is only 2 months of rental fees.

      Definitely get rid of that rental fee. At $14 a month, that money could be put to better use.

      Stay safe, John.

  4. Hi there. I have a 200 mbps plan that somehow does not work well in a bedroom about 20 feet from the modem/router (currently Xfinity combination) when another device is in use in the main room. My place is small, but we may move into a bigger space, and also have completely embraced a lot of smart home technology. Looking to rid myself of internet issues, I am thinking of upgrading speeds with my ISP and definitely want to purchase my own separate modem and router. Is gig internet and DOCSIS 3.1 overkill? How long until 3.0 is obsolete or just not good enough anymore? And also when is a normal time to replace a router or modem – do they dependably last 5 or so years? Thanks!

    • Hello Matt,

      Gig internet and DOCSIS 3.1 is only overkill if you don’t plan on upgrading to that speed in a few years. DOCSIS 3.0 won’t be going away for several years due to the slow implementation of DOCSIS 3.1 in the USA region (most people don’t have access to DOCSIS 3.1 speeds).

      Keep in mind, faster speeds may not fix your WiFi issues due to building materials in your home or interference from other electronic devices. You could certainly try a faster speed, but just be mindful it may not fix your issue. Hard wire (connect an Ethernet cable) when you can. You should only need to replace a modem or router when you want faster speeds. These devices are really dependable since they have no moving parts. As long as they stay cool, your devices should give you a decade (or more) of dependability.

      Hope that helps you. Stay safe, Matt!

  5. I have Centurylink internet service & they say my modem is outdated. They suggest me getting another modem thru them & upgrading my internet speed but a family member suggested purchasing my own modem. Any suggestions??

  6. I just set my parents up with xfinity cable and internet package. They need to purchase a modem and router. I have looked over the approved list that xfinity provides. However, I am confused. Are the modem and router separate from each other, as in we need to purchase 2 different devices? The internet plan they have is only 100Mbps. The only devices they use are 2 cell phones and the smart tv. Can you suggest what to purchase for the lowest cost but sufficient enough to run what they need it to? Thank you!

    • If a modem is on the the approved modem list marked as having WiFi, it means the device is both a modem and router combined into one box.

      Based on what you asked for, the TP-Link Archer CR700 is the cheapest device. The CR700 contains a WiFi router and the device is capable of faster speeds than what you parents currently have, so if they ever get their speed upgraded, the CR700 will still be able to handle it.

      Hope that helps, Jennifer.


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