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Modding the modem; Cooling the cable connection.

Modding the modem; Cooling the cable connection.

Editor’s Introduction.

Many of us spend hours adding fans to our PCs and searching for the best heatsink. This is all in the quest to cool. A cool PC is more stable and provides for more headroom to overclock but what about outside of the box? How many have thought a ADSL/DSL modem could generate enough heat to cause instability? We went where others haven’t looked and packed on additional cooling power to, of all things, the modem.

And now Geeky1 takes us where we never thought to look.

Lately, my DSL modem has been dropping connections inexplicably. When I went to reset it, it was always fairly warm. Now, being the cooling forum mod that I am, the first thing that came to mind is that the flakiness must be heat-related.

And, with that hypothesis, I set out to “fix” my DSL modem.

Disclaimer: Opening your DSL modem will almost certainly void your warranty, and could kill the modem. If the modem is leased, your ISP will most likely not be thrilled to discover that you’ve disassembled their DSL modem for them, either. Neither the author nor www.short-media.com will be held responsible should you attempt this mod and something goes wrong.


My first challenge was figuring out how to get into the stupid thing. I pulled off all 4 of the foam padded “feet” expecting to find screws under them. It was a no go (or show) so I figured that since I could get a replacement DSL modem for $5 (surplus stores are wonderful things) I’d just grab a flathead screwdriver and pry it apart. I managed to get the edges of the top and bottom pieces of the case apart this way, but it wouldn’t come apart. So, I came to the conclusion that there must be something else holding it together. I started poking around at the label on the bottom looking for the screw(s) that hold it together and there it was hiding under the label at the centre of the bottom of the modem case.


Once that screw came out it was just a matter of pulling the two halves apart.


Having successfully exposed the PCB I simply plugged the power and the data cables back in and turned it on to check to see if it still worked after my chisling and prying. (Remember: This is a live electrical device and things could go ZAP…especially YOU! Do so at your own risk!) It did and I used it normally for a little while to see (or rather feel) what the heck was getting so warm. I found that one chip in particular, the one in the bottom right corner of the above picture, got significantly warmer than anything else in the case. My digital multi-meter, which has a type k thermocouple attachment, registered temperatures of approximately 125*F (52*C).

In the grand scheme of things this is not all that hot. Intel gives an absolute maximum case temperature (the bga package the chip is in, not the actual modem case) of 221*F (105*C) for the i810 chipset. (source: Intel(R) 810/810E Chipsets: GMCH Electrical and Thermal Specifications Datasheet Addendum. On a similar note I just recently proved that palomino-core Athlons are quite capable of chugging along at 176-194*F+ (80-90*C) without suffering any apparent ill effects.

125*F may not be all that hot but I suspected it may be hot enough to cause the chip in question to error out thus crashing the modem. I also suspected that it may be hot enough to warrant additional cooling by way of a heatsink or two. There were a number of other chips on the PCB that also got noticeably warm so I decided that I might as well go ahead and heatsink those chips they too were exposed.


I used a few black-anodized aluminum 13mm square heatsinks with pre-applied thermal tape that I had sitting around. I cleaned the modem chips with isopropyl alcohol and let the alcohol evaporate before attaching the heatsinks.


That’s it.

I just put the modem back together and I was done. Now comes the all-important question; did it work? Apparently it did. The freezing and general flakiness I had been experiencing stopped. Now maybe the phone company was having line problems but, to be honest, I never checked. Regardless the modem is not likely to suffer from heat-related problems in the future.

I know that some of you are thinking “maybe cooling the modem down would make it faster too!”. I thought of the same thing so I ran a few benchmarks.


The short answer to faster upload or download speeds is no. I tested the speed by going to DSL Reports and running the speed test one time from each of the 3 servers and then averaged the results. The speeds after the modem had warmed up were slightly higher with more cooling but this could very easily be due to a lighter load on the servers during testing. Beyond that the difference in speed is so small as to fall well within an acceptable margin of error for a typical bandwidth test. The only conclusion I can come to is that cooling the modem will not make your internet experience any faster but if the modem is consistently dropping connections or being generally “flaky” then improving the cooling may help.

Editor’s thoughts

The article clearly shows that heat is the enemy of any electronic component. It is a well-known fact that heat can be a likely culprit behind a PC that is experiencing instability or random freezing. Who would have thought to look at a simple modem as a device which could overheat? One of our Short-Medians…that’s who. I suspect there’ll be a fan modification somewhere in the future and perhaps some neon. Happing moddin!


  1. fatcat
  2. MediaMan
    MediaMan damn...soon as I edit an article....link goes away..back now. (Add to the site glitch pile)

    Ya know...it's a durn interesting piece by Geeky1. Simple but a "who'da thunk it?". :)
  3. Geeky1
    MediaMan wrote:
    Ya know...it's a durn interesting piece by Geeky1. Simple but a "who'da thunk it?". :)

    Thanks. :)


    Ya know... I took apart my routers, too (a Linksys 4 port 10/100 thing, and a D-Link 4 port 10/100 + 802.11b (22Mbps "turbo") thing) but didn't find anything that got hot enough to heatsink. :( I opened up the vents on the D-Link to allow air to flow more freely through it anyhow, though... :D
  4. BlackHawk
  5. Geeky1
    Geeky1 Do NOT give me ideas.
  6. Leonardo
    Leonardo I like it. Great things have been accomplished simply because someone became curious. 'What if...' and all that.

    Modem on a half shell. Add some nuts and bananas.
  7. Tex
    Tex I don't own it anymore but the old fiber gigabit rack mount switch I had was the second loudest piece of equipement I had in my rack. It was meant for noisy computer rooms and big ass fans that were loud as h*ll

  8. Geeky1
    Geeky1 I've got a 3Com 24 port rackmount 10/100 hub (switch?). Loud as hell. I still haven't figured out how to get it open, either... :-/ :D
  9. Leonardo
    Leonardo Try a hammer and wood chisel.
  10. KingFish
    KingFish This will get it open

  11. QCH
    KingFish wrote:
    This will get it open


    Flame is too yellow.... Nice blue flame with a small light blue cone. That's Hot...

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