Reliable 25 Gigabit Ethernet via Thunderbolt

kohlschuetter.github.io

254 points by kohlschuetter 5 days ago


throwaway2037 - 18 hours ago

This is an outstanding blog post. Initially, the title did little to captivate me, but the blog post was so well written that I got nerd-sniped. Who knew this little adapter was so fascinating! I wonder if the manufacturer is buying the Mellanox cards used from data center tear-downs. The author claims they can be had for only 20 USD online. That seems too good to be true!

Small thing: I just checked Amazon.com: https://www.amazon.com/s?k=thunderbolt+25G&crid=2RHL4ZJL96Z9...

I cannot find anything for less than 285 USD. The blog post gave a price of 174 USD. I have no reason to disbelieve the author, but a bummer to see the current price is 110 USD more!

omgtehlion - 18 hours ago

Ha! Been running these for years on both linux and windows (on lenovo x1 laptops). Using cheap chinese thunderbolt-to-nvme adapters + nvme-to-pcie boards + mellanox cx4 cards (recently got one cx5 and a solarflare x2).

Pic of a previous cx3 (10 gig on tb3) setup: https://habrastorage.org/r/w780/getpro/habr/upload_files/d3c...

10gig can saturate full speed, 25G in my experience rarely reaches same 20G as the author observed.

zokier - 20 hours ago

Note that you can do point-to-point network links directly with thunderbolt (and usb4).

https://support.apple.com/guide/mac-help/ip-thunderbolt-conn... etc

icelancer - 6 hours ago

I've had a lot of problems with even 10GbE via Thunderbolt 3/4. Bandwidth-wise it works fine, but latency and jitter are issues. This means that stuff like high-speed cameras that need to be synchronized over Ethernet using Precision Time Protocol (PTP) tend to simply fail with these devices.

consp - 20 hours ago

I'm surprised you are only getting 20gbit/s. I did not expect PCIe to be be the limiting factor here. I've got a 100gbit cx4 card currently in a PCIe3 X4 slot (for reasons, don't judge) and it easily maxes that out. I would have expected the 25g cx4 cards to be at least able to get everything out of it. RDMA is required to achieve that in a useful way though.

Edit: forgot is isn't "true" PCIe but tunneled.

userbinator - 21 hours ago

Thunderbolt is basically external PCIe, so this is not so surprising. High speed NICs do consume a relatively large amount of power. I have a feeling I've seen that logo on the board before.

Nextgrid - 20 hours ago

Neat, but the thermal design is absolutely terrible. Sticking that heatsink inside the aluminum case without any air circulation is awful.

whatever1 - 14 hours ago

Any idea why ethernet stagnated in terms of speed? There was a time it was so much faster compared to usb. Now even wifi seems to be faster.

Sure one can buy nice ethernet cards and cables, but the reality is that if you grab a random laptop/desktop from best buy and a cable, you are looking at best at a 2.5Gb/s speed.

drnick1 - 15 hours ago

I used to have an SFP28 Mellanox card in my home server, but went back to a simple 2.5G Ethernet port for the LAN side. The Mellanox card ran hot and needed an extra fan near it to dissipate the heat. It was cool but there was no real benefit other than occasionally when transferring some large files.

Until motherboards include SFP ports it's probably not worth the effort at all in home setting; external adaptors like the one presented here are unreliable and add several ms of latency.

thadk - 16 hours ago

Does this manufacturer's practice pattern of repackaging data center components (e.g. Mellanox) imply any up and coming product creation opportunities?

shantara - 15 hours ago

That is really cool to read. And here I am, still running my home network on a measly 1Gbit Ethernet. I considered upgrading, but the equipment power consumption even when idle makes it an expensive proposition to consider just for fun.

project2501a - 18 hours ago

nitpicking but why would someone type `sudo su` vs `sudo -i`

madduci - 19 hours ago

I still have issues under Linux (Kernel 6.14) and Thinderboldt 4 docking stations. The simply don't get recognised.

But this is a cool solution

mrbluecoat - 4 hours ago

Is this satire?

> All other 25 GbE adapter solutions I’ve found so far ... have a spinning fan. ... the biggest downside of the PX adapter is that it gets really hot, like not touchable hot. Sometimes, either the network connection silently disappeared or (sadly) my Mac crashed with a kernel panic in the network driver. ... Other than that, the PX seems to do the job

bob_theslob646 - 7 hours ago

Please forgive me for my ignorance, but are there currently any ways of being able to write data down at that speed? I see 2026 PCIe 5.0 NVMe advertising theoretical 14gb/s but not sure how feasible even that is.

the_real_cher - 8 hours ago

> the biggest downside of the PX adapter is that it gets really hot, like not touchable hot. Sometimes, either the network connection silently disappeared or (sadly) my Mac crashed with a kernel panic in the network driver. Apple has assured me that this was not a security issue. Other than that, the PX seems to do the job.

Made me chuckle.

cyberax - 10 hours ago

Ha. I got one of the 10G Thunderbolt adapters a several years ago. And eventually started having problems with Zoom calls around noon. With dropped connections and stuttering. Zoom restarts usually fixed the problem.

After it happened 3-4 times, I started debugging. It turned out that we usually get at least a bit of sunlight around noon, as it burns away the morning clouds. And my Thunderbolt box was in direct sunlight, and eventually started overheating.

And a Zoom restart made it fall back onto the Wifi connection instead of wired.

I fixed that by adding a small USB-powered fan to the Thunderbolt box as a temporary workaround. I just realized that it's been like this for the last 3 years: https://pics.ealex.net/s/overheat

cs02rm0 - 21 hours ago

Now I just have to contrive the circumstances where this is useful to me. :)

otterpro - 19 hours ago

> reduces temperatures by at least 15 Kelvin, bringing the ambient enclosure temperature below 40 °C,

I had to do a double-take when it mentioned Kelvin since That is physically impossible.