10Gb/s Ethernet: switching to a Broadcom SFP+ module

Back in April, I upgraded my home LAN to 10Gb/s. The in-wall cabling is CAT-6 or similar, so I had to use 10GBASE-T. Now, the router I'm using, and the switch in my study, provide 10Gb/s through SFP+ cages; that meant that they needed 10GBASE-T SFP+ modules in order to connect.

That kind of module is known to run hot -- sometimes too hot to actually work. The modules in reggie , the router, appeared to be running OK (see the linked post above for charts), but the one in nigel , the study switch, was a worrying 93C. I tried sticking some mini-heatsinks on it, which seemed to help a bit. But the weather got warmer, and eventually the module overheated. I lost access to the Internet from the study, and checking the metrics showed me this:

You can see that it's "flapping": the temperature gets up to a level where the module shuts itself down for its own protection -- about 95C, I think -- and then when it has recovered, it switches on again, the temperature rises, and the process repeats.

I was able to work around the problem by switching on the air conditioning in the study. But normally I only have it on when I'm in there, and keeping aircon on 24/7 just to keep the network working felt like the wrong solution.

It was time to switch to a more power-efficient SFP+ module.

My original 10Gb/s post had quite a lot of discussion on Hacker News, and xxpor mentioned that there are two generations of 10GBASE-T SFP+ modules: old ones using a Marvell chip, and newer ones using one from Broadcom. blunden on the ServeTheHome forums made the same point. The Marvell-based ones were known to run hot, and they both recommended finding Broadcom-based ones.

I'd confirmed that the MikroTik S+RJ10 that I had in nigel was indeed a Marvell one, so the solution was pretty simple: get a better one. So I went on Amazon and picked up a 10Gtek ASF-10G-T80-INT. Checking 10Gtek's own page on that module confirmed that it used the right kind of chip (although it was a little bit garbled):

10Gtek's ASF-10G-T80 is a newest version copper transceiver, its biggest feature are ultra lowpower consumption and longer transmission distance (1.6W C10Gbps 30m，2.0W 110Gbps 80m). ASF-10G-T80 is a 10GBase mult-rate Copper RJ45 SFP+ transceiver, designed in with BROADCOM BCM84891 PHY chip following IEEE 802.3an/az and SFP+ MSA, supporting up to 80-meter transmission over CAT.6a or CAT.7.

A day or two later, it arrived. It came in a rather pretty little metal case:

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