Hacker News Reader

Comment by JoshTriplett | Hacker News Reader

> However, when it comes to 2.5G, I struggle to find one good reason to use it; such a tiny step-up in bandwidth, and for what?

Portability and heat. You can get a small USB 2.5G adapter that produces negligible heat, but a Thunderbolt 10G adapter is large and produces a substantial amount of heat.

I use 10G at home, but the adapter I throw into my laptop bag is a tiny 2.5G adapter.

View on HN

I’m sure it depends on the model, but in my experience if you force a 10G copper transceiver to 2.5G the insane heat generation goes away. I don’t have any Thunderbolt 10G adapters, but I’m kind of surprised they’re much larger. A SFP+ transceiver is the same size as a SFP one.

I think a major reason for the size is for heat dissipation, because it has to be prepared to handle the heat of a full 10G copper connection. Mine runs hot.

Most of my cables coming out of the aggregation switch are DAC and fiber, but there is no 10G copper because my PC came with 10G copper NIC integrated. Anyway, the difference in heat between this transceiver is shockingly large.

I knew it runs hot before I deployed it, but I wasn't aware that you have to wait for it to cooldown before unplugging, or you get burnt.

The power has come down a lot and drops in shorter runs, from ~15w per port at the max 100M cable length back in 2006, to ~2w with todays tech and short cable run.

There's of course fiber too...

Reply on news.ycombinator.com