Giles' blog

10Gb/s Ethernet: using mini-heatsinks with a 10GBASE-T SFP+ module

In my last post I showed the somewhat-scary temperatures I was getting on the MikroTik 10GBASE-T SFP+ module I have plugged into nigel, the 10Gb/s switch I have in my study. As I mentioned then, the plan was to try using some of the mini-heatsinks that people use on Raspberry Pis, to see if that would help.

Here's how it went.

I bought a 40-piece set of heatsinks made by the improbably-named VooGenzek on Amazon for €8, and attached two of them like this -- see the bottom module, with the yellow cable:

That was 24 hours ago, and here's a chart of temperatures from that module showing the 24 hours before and after:

You can see the big drop-off in the middle of the chart; it even overshot a bit (I'm guessing because the heatsinks absorbed a bunch of heat initially when I put them on).

The difference looks more dramatic than it is! See where the Y-axis starts. But given that the weather has been pretty much the same today as it was yesterday, that looks like a 3.5°C improvement. Not great, but not nothing either.

In the copious discussion about the last post on Hacker News, one of the most popular comments -- from xxpor -- was that there are two generations of SFP+ modules for this kind of thing; an older one, using a Marvell chip, and the newer one using one from Broadcom. blunden on the ServeTheHome forums made the same point. They both mentioned that a good indicator of which type a module is using is that the older ones tend to be rated up to 30 metres, while the newer ones are rated up to 100.

This one is a MikroTik S+RJ10, which definitely is one of the older ones -- the specific chip is mentioned in the docs. I'm not sure which chip the Protectli modules in my router reggie are -- they're these modules -- but they say they're rated up to 30 metres, so I guess they're probably the older type too.

Looking into switching those out might be a good next step! I probably won't do that in the short term, though, unless I start getting issues as we move into summer.