cable modem – Monoprice Molded Modem Cable – 6 Feet, DB9 Female to DB25 Male for $5.99

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A MODEM SERIAL CABLE enables two DTE or DCE devices to communicate with no conflict in data transmission.

cable modem – Monoprice Molded Modem Cable – 6 Feet, DB9 Female to DB25 Male for $5.99
cable modem – Monoprice Molded Modem Cable – 6 Feet, DB9 Female to DB25 Male for $5.99


  1. I have xfinity performance pro which is rated for 150 mb/s down and 5 mb/s up. I’ve been using the Arris SB6141 modem which is 8 channel down x 4 channel up, great modem, no issues but it’s speed maxed out at 120 mb/s down and 5 mb/s up. I figured what the heck might as well get the speed i’m paying for, so I purchased the Motorola SB7621 which is 24 channel down x 8 channel up. Internet speed is now 180mb/s down and 6mb/s up with a ping of 19ms. I am happy that I am now getting the speed I am paying for. Yes the upload speed didn’t change much but that is because xfinity does not support 8 channel up in my area. This means even though this modem supports 8 channel up it only shows 4 active up channels when you log into it, this is not the modems fault, this is xfinity’s doing. The download channels are fine, all 24 channels show up and are active. Yes, I could have purchased a 16 channel down and 4 channel up modem and received the same current speeds but at the time of purchase this modem was less than or the same amount as all the 16 x 4 modems. By buying this Motorola I can upgrade my internet speed down the road and still be covered. Another good thing is that this modem has the Broadcom chipset not the Intel puma.The modem comes with good instructions and is well packaged. Setup was a breeze. I didn’t have to call xfinity. All I did after I hooked up just the modem to my PC was navigate to which brought up the xfinity activation page. Then just log in with your xfinity credentials and follow the prompts. Very easy and welcomed as I didn’t want to sit on the phone talking to xfinity support.I never do reviews but I figured this little box deserved one and hopefully this helps someone.

  2. Five minutes after arriving on our doorstep, the new cable modem is up and running. Bracing myself for difficulty with Comcast, I was pleased at how easy setup was without ever having to speak to Comcast’s clueless CS. Using a laptop with an Ethernet jack, here’s how easy it was:1) Wrote down my Comcast account number (This is the MOST important step!!!)2) Connected modem to cable, power, and phone line3) Connected Ethernet cable to modem and computer4) Waited three minutes for the first three lights to blink steady (they’ll blink and flash while the modem is syncing. You could wait up to 10 minutes for sync).5) Turned off WiFi6) Opened web browser, and Firefox had a nice little ‘show login page’ button appeared (if this doesn’t show, you can go to Entered my account number and street address8) The modem reset itself. I plugged that into my Luma and we were off to the races!Ironically, Comcast sent a new tower modem a week ago. I don’t know if it’s me, but this seems faster than that did – speed about the same but ping time is now 9ms instead of 14 and pages that seemed to load slowly before pop in immediately. Biggest bonus is that we’re saving $11/month going forward.UPDATE: 4/5/18 – Everything was working perfectly until Comcast turned off my service this weekend because the modem wasn’t registered in the right database and Comcast thought I had no equipment. Object lesson: After activating online, call Comcast to make sure the equipment has registered across all of their databases – 5 minutes could save you 2 hours! The modem, however, is working flawlessly and I still highly recommend it!

  3. This cable modem is a beast (in a good way)! A little over 7 years ago, I bought the Motorola SB6120 to replace the crummy cable modem that Comcast charged me monthly to use. I had no problems with the SB6120, but got an email from Xfinity saying I needed to upgrade my equipment. I guess because they have increased the speed on my service and the SB6120 is so old it may not be supported with updates from Motorola. OK…I paid $75 for the SB6120 and it probably saved me over $750 in monthly rental for 7+ years.Decide first if you want DOCSIS 3.0 or 3.1 because the Docsis 3.1 is new and will probably be usable for years to come. Motorola only has 1 Docsis 3.1 cable modem available today which is the MB8600 and is almost twice the price of the Docsis 3.0 MB7621. If you compare the specs, the MB8600 is faster but at nominal 1000 Mbps and Comcast certified 400 Mbps, the MB7621 is way faster than my 150 Mbps service.I got it today and got it activated and hooked up to my new Motorola MR1700 router. The process was fast and easy if you can figure what they are trying to say in the quick start guide. I activated with my notebook directly connected to the cable modem and the speed exceeded my 150 Mbps service by almost 30%. After direct wire of my notebook through the router, my speed was also exceeding my service speed at the same level.The only way I can lose on this purchase is if Docsis 3.0 becomes obsolete in less than 8 months and I’ll bet that is unlikely.

  4. i am going to repeat what another buyer said.. I am replacing this with the SB6183. I had the same exact problem as the other buyer posted exactly0 I am past my return date also so I am out $100.Do not buy this modem. This modem is running on a flawed Puma chipset and is plagued by continued disconnects. 8 of 10 times it recovers after 30-60 seconds, the other 2 you will have to bounce the modem. I did quite a bit of troubleshooting, first thinking this was my wifi router, then going after my ISP. but the issues turned to be due to this faulty modem. I’m unfortunately now outside of the return window, so I’m stuck with a $100 paper weight, as I’m buying a different modem to replace it. Why is this still being sold is beyond me.

  5. Reply
    Audiophile Headcase
    June 7, 2018 at 12:00 am

    This Motorola MB7621 cable modem was a huge disappointment. I bought it to replace my four year old Arris SB6141 which is a 8×4 modem. The MB7621 is 24×8 so in theory it should give better performance. However, the performance I saw was much worse than the older SB6141 with download speeds. I have Comcast Performance Pro 150mb service and was routinely seeing about 100mb in real life with the old modem. When I put this new cable modem on the coax the download speed consistently dropped to about 32mb. The signal levels all looked good and there weren’t any uncorrected codewords. It appeared that 23 of the 24 available download channels achieved a lock. After spending several hours playing around with settings, etc, and chatting with Comcast “support” (useless) I had to assume that it was somehow defective. Back to using my trusty old Arris SB6141, hopefully for a few more years. I noted another reviewer also saw speed slowdowns on this modem. Even though it is listed as being Comcast Xfinity compatible it certainly did not work for me.

  6. The Netgear CM600 cable modem is an ultimately reliable DOCSIS 3.0 cable modem for service speeds up to 300 Mb/sec or faster. Unlike the company’s CM700 model, it does not incorporate the troublesome Intel Puma 6 chipset found in many higher-end cable midems, making it a more reliable choice.There may be a downside for some, having little to do with the CM600. When accessing the CM600 interface, it is noted that ALL firmware upgrades can only be provided by the ISP (in my case, Spectrum). Whether Spectrum will upgrade said firmware (when and if necessary) is questionable, though it would be to their advantage.It has also been explained that Spectrum cannot remotely troubleshoot issues in “non-standard,” cable modem/routers. These being anything other than the standard free cable modem/routers Spectrum installs as part of their service. They can, however, initiate a reboot and validate that the CM600 is functioning.Funny, this seems more like a positive for me! As a trained network support technician, I like the idea that Spectrum cannot manipulate the settings of either my modem or router; something I am more than capable of doing on my own.Setting up the Netgear CM600 cable modem is as easy to setup as plugging it in and turning it on. The CM600 was fully functional within seconds of connecting the Internet cable to the back.The CM600 is a one-trick pony; it is a cable modem and nothing else. It converts cable data into Internet data. Given the specifications and the high-quality components it does its particularly job incredibly well. The CM600 is built to pull a signal out of a weak or “noisy” line. It will continue to provide Internet service when other lesser modems will drop out. Since purchasing this modem, I have had no random cable dropouts from my ISP. Remember, it has no built-in wireless or wired router. Such a router must be purchased separately.A quick aside: The router is the Grand Central Station of your home’s WiFi universe. It takes a tremendous amount of efficient but fast processing power to send and receive multiple data streams quickly and effectively between a houseful of smartphones, smart HDTVs, computers, tablets, cameras and other WiFi-enabled gizmos and the Internet. A router is a radio transceiver. The more powerful it is, the more information it can send through the air over longer distances. The more sensitive it is, the more it can pick up data being transmitted 500+ feet away. To get the best benefit from your Netgear CM600, I recommend the Netgear Nighthawk® R7000P. Built to handle the needs of the tech enabled home, it is a stellar dual-processor performer at an incredible price.No. I don’t work at Netgear!

  7. This modem was great and behaved exactly as advertised, but only for two months. I started to notice spotty internet last week and blamed it on Comcast and then my internet went completely out 3 days ago. All the modem lights were on, my router was working fine, but I couldn’t get internet. The Comcast technician came over for an hour today until we finally realized the modem wasn’t responding correctly so I replaced this with my old modem and got my internet back.So there you go bought Jun. 13, officially dead Aug. 14. Outside of the return period and now I’m stuck with a paperweight. The technician also warned me against Netgear modems too, he said they tend to fail earlier. I do NOT recommend getting this you can get cheaper more reliable modems (Arris). Thanks Netgear for disappointing me, you’ve lost a fan.

  8. I purchased the Arris SB8200 for Xfinity Gigabit Internet service as they have a deal for two years for the same price as the 400Mbps plan ($69.99). So in order to save almost $15 a month I decided to buy my own modem to replace my aging Motorola (Arris) SB6141. My SB6141 netted me 259Mbps down and 35Mbps up on my previous plan of 400Mbps down and 35Mbps up, which is great for a 8×4 channel Docsis 3.0 cable modem. So since Arris bought Motorola modem cable division I decided to get another one having had a great product with the 6141. The Arris SB8200 is also the only Docsis 3.1 modem with two Ethernet ports capable of doing 2Gbps down and is the most future proof of any modem on the market at the time of writing this review. And you can get a refurbished model for half the price which is even better!Inside the Arris SB8200 is a Broadcom BCM3390 chipset (a much needed change from the SB6190’s Intel Puma 6 chipset which had hardware bugs and caused them a lawsuit for good measure), 3GB of RAM, 128MB S34ML01G200TFV00 Spansion flash memory NAND and 16MB Macronix MX25L12805D SPI NAND flash memory. The SB8200 is capable of downstream bonded channels up to 32 SCQAM or 2 OFDM and upstream bonded channels up to 8 SCQAM or 2 OFDMA (32×8 SCQAM and 2×2 OFDM). The Ethernet ports are only Gigabit Ethernet and therefore the Max you will get is 950Mbps average down and it will never be possible to the the boxes 10Gbps selling spiel. Even if you don’t have Docsis 3.1 in your area or a Gigabit internet speed plan this modem will serve you for many years to come. And this modem has 3GB of RAM, which the other Docsis 3.1 modems have 256MB or less! RAM! Oh and with most providers (Xfinity included) you can call them and add a separate IP address for the second Ethernet port for a small fee (Xfinity charges like $5.95 if I’m remembering correctly). This would be great if you wanted to connect a gaming console directly to the modem for the best speeds and then connect your home router to the second. And eventually you’ll be able to kick in 2Gbps by merging those two Ethernet ports!Setup of the device was quick and easy and you simply plugin the coxial cable, Ethernet cable to your device (router for 99% of the people) and power cable and you are off and running. A quick call to your internet provider (Xfinity for me) to add the HFC MAC address and the modem is registered and provisioned and I’m up and running within ten minutes. Xfinity will try to send out a tech but you can get them to override it if you know what you are doing. Gigabit internet can be extremely temperamental as we’ll discuss later which is the reason Xfinity requires sending out a tech on all Gigabit plan installs. And again this is simply a modem so you will need a router if you want wifi or the ability to connect more than one device.The performance of the Arris SB8200 is top notch and I was easily able to pull my provisioned modem speeds from my Xfinity service. I was able to test 1.4Gbps down ( also includes backend speed as actual can only be 950Mbps as I mentioned above) and 45Mbps up. On my tests are almost always 930-960Mbps (or near that) down and 40-50Mbps up. These speeds are AMAZING and just my upload speed is faster than most people’s download speeds! Right now Xfinity is only utilizing Docsis 3.1 for the downstream channels so the modem lights will have a blue light for downstream and a green light for upstream (this is not an error or bug).My issues arose with my Xfinity service and resets, slow speeds (300Mbps Max down), etc. Xfinity sent out a tech and that did nothing. So another rech came and found a ton of ingress coming from 4 lines on my tap. He trapped them off and I was up and running with Gigabit speeds again. Then the resets started, at night almost every 10 minutes! It was only happening between 10pm and 7am average, EVERY NIGHT! I had more techs out, supervisors and more supervisors! After a month (and many hours of my time and speaking up) the issue was resolved as it was a bad line amplifier which was causing noise and caring my upstream to spike into the high 50s, which triggers resets on the modem and t3/t4 errors. Now my neighbors were having issues on certain channels and slow internet but their modems WERE NOT RESETTING! And we knew my modem wasn’t bad as it was fine for over 12 hours a day with no errors at all in the log until night began to fall everyday. And In fact my neighbors never lost internet, EVER but my internet was almost useless at night time. So the Arris SB8200 is extremely sensitive to t3/t4 errors and the threshold for errors and resets is much higher for the Xfinity owned gateways and modems. Also Arris had out out a firmware update previously about severe sensitivity to t3/t4 errors and I had the latest version but I was still having issues so they still need to work on this. If you are experiencing issues with your Arris modem navigate to and you’ll be able to see basic signal information, modem error logs, modem and firmware info. You can use this information and post it in the support forums to get help and diagnose any problems.But now that the line and backend errors are corrected it’s smooth sailing and I’m saving myself a ton of money (the new Xfinity modem charge is $14 plus tax and it will be $15 by the beginning of 2020 so you pay for the modem in a little over a year) every year and you’ll have the newest technology that is even better than the Xfinity modems and gateways, many of which use the Puma 6 chipset which I mentioned above (causing severe lag and timeouts which can kill online gaming or video watching). So I’m paying $69.99 and getting Gigabit speeds of 950Mbps down and 48Mbps up which is a great deal hands down and you won’t find speeds that cheap ANYWHERE ELSE! The Arris brand is keeping the Motorola spirit alive and kicking which is great for competition! The Arris SB8200 is the best modem you can buy for your money right now and if you can find a refurbished unit on Amazon even better (they didn’t have any when I bought mine but three weeks later they did and for $100 cheaper)!

  9. DON’T BUY THIS MODEM. I’m so surprised that I experienced all of the same issues as the other negative reviewers. I ordered this modem because of a notice from xfinity that the DOCSIS 3.0 modems were no longer being supported (or something like that). Having a used SB6121 for about 5 years, which was still running great, I thought it was a good opportunity to upgrade, especially since I have had such a good experience with the older Surfboard modem. I had the modem for about 4 months, and suddenly it locked up on me, and we were out of internet for a couple of days. A lot of people seemed to have the same experience after 4-6 months. This also happened coincidentally after I came back from vacation. It seems like it it has happened to some others who gone on vacation to find their SB8200s locked up. Maybe it has to do with the overheating issue? But for 2 days, an ISP tech visit, hours of back and forth calling with xfinity support and Arris support, we determined it was the modem. This WASTED SO MUCH TIME. I was looking forward to getting some work done before returning to work after vacation. Instead I was on the phone and with a technician throughout the better part of my whole weekend. Arris support was the worst. They refused to acknowledge my issue and tried to hurry me off the phone, throwing the ball back at the ISP. I told them my old modem worked right away after activating it back. They said they could not continue to troubleshoot unless I reactivated the new (SB8200), so again I had to call the ISP to switch back to a non-working modem, taking me offline for another few hours. With each call I had to repeat the same troubleshooting steps. Doesn’t the customer support communicate with one another? Finally, on my third call Arris determined it was the modem and gave me the options for a replacement. The standard option requires you to send it back first, before getting the replacement. Give about 2 weeks for this. The advanced option lets them send it to you within 7 days for $15. The expedited option is $50. I chose the standard option. But really, I want my money back. I don’t want another unit I can’t trust, and I have to wait over 2 weeks for it. Unfortunately it failed outside of the Amazon refund window. After all of these negative reviews, I would hope Arris recognizes the problem with their units and somehow communicate to their customers they are working on improving it. I don’t think this should be an Amazon’s choice product anymore. I really felt let down by this one. I’m going to wait for the replacement unit, hopefully it doesn’t fail again in another 4 months and require 12 hours of customer service to get another unit.

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