WRT54G: CPU cooling mod

I’ve been working on one of my WRT54G boxes. For those that don’t know what a wrt54g is, you just lost major geek points. But, I’ll fill you in for the future; Linksys (now part of Cisco) makes an awesome little box for home/small office wireless use. The reason they have gained so much fame among geeks is that Linksys released the source code for the boxes firmware. This spurred on countless projects revolving around the wrt54g.

I’ve been using the DD-WRT firmware on most of my WRT54G’s for some time. Recently I went through my once every so often firmware update cycles. Getting new firmware on all my wireless equipment is quite a project.While I had one of the 54Gs off the air I decided to make some upgrades. The goal, was to overclock the CPU and while I was at it, crank up the power a bit more. Out of the box, the units run about 25-30mw. The radio in the unit will run over 200mw. I usually turn them up to 50 without modification. In a cool environment you could do 100 without a cooling mod.

More importantly is the CPU. The unit has a Broadcom processor in it running at 200mhz. It’s reported that some of the newer models run slightly overclocked (216mhz) to fix a bug, this factory OC is without modification.

The unit I’m working with in this article should be able to run stable up to 300mhz. However cooling does become an issue. I dug through my parts bin and found a chipset cooler and a couple appropriate sized heatsinks; I took the radio off the air and started working.

Once you’re inside the wrt54g you’ll see two main chips as well as a rf shieded metal compartment for the radio. Of most concern in the overclocking is the cpu. It’s labeled “broadcom.” Apply some thermal grease or thermal adhiesive and mount the chipset cooler to the CPU. In my case, I don’t plan on making any mods to the case. The chipset heatsink with fan will easily fit inside the stock case without modification. Airflow is sufficient due to the clearance between the fan and case. For most applicaitons putting a chip cooler or heatsink on that would suffice. But them I’m not most people. I have noticed that the ethernet switch controller gets a tad toasty after heavy lan file transfers. So I put a simple heatsink on this chip, again use some from of thermal layer.
All that left is the radio. Having air moving in the compartment (as a result of the cpu cooler) will help, how much? we’ll see. I’ll be monitoring the temp of the radio at 100mw for the next few hours while I’ve got the thing under a load then decide if I wan’t to crack open the rf shield and make some cooling mods. I’ll post later today, if I do.

WRT54G

Above is a picture of the board with the mods made, I used thermal tape instead of grease, I needed the adhiesive to hold the sinks on, since the board isn’t meant for this application. For what it’s worth, the sink on the switch controller is overkill. But it’s the size I found while digging in my boxes. I think the cooler on the cpu is perfect for clocking speeds up around 300mhz.

WRT54G up close

And here’s a closeup.

The wrt54g can be picked up at most retailers that have wireless networking equipment. Expect to pay $40 online and $50 instore at most national chains. Once modified, your wrt54g becomes capable of many things normally only found on higher end routers. There are several versions of the wrt54g and similar newer models. Visit any of the third party firmware sites for info on the specific versions/models to make sure what you buy can will do what you want it to.

UPDATE: no, I haven’t found the need to do an RF cooling mod. But I plan to anyway. I believe that using some nonconductive thermal foam or thick thermal adhiesive tape would bridge the gap between the RF board and the metal shield. If I can do that, the added heat dissipation of the metal shielding should be more than enough. Oh and yes, I love the wrt54g, but then again… what geek doesn’t?

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