Misadventures with Thunderbolt

The Promising Technology

Thunderbolt is a port technology by Intel, and first appeared on Macs in 2011. Originally, the primary use for Thunderbolt was as a video port (mini DisplayPort), though there were some other peripherals, such as external storage. With Thunderbolt 3, things got very interesting. The connector switched to USB Type-C, and the port included USB compatibility. The peak bandwidth was also increased to 40Gbps, opening up many possibilities for extremely high bandwidth devices such as external graphics. Even better, Thunderbolt 3 could deliver up to 100W of power, either to devices attached to the computer, or to the computer from the attached device.

On paper, things sounded amazing. Reality, as is often the case, was quite a bit different.

In 2016 I purchased an Asus GL702VM gaming laptop. Asus proudly advertised "Onboard Intel® Thunderbolt™ technology" that "gives you single-cable data and signal transmission rates of up to 40Gbits/s". I had kept my previous gaming laptop for 4 years, and the only reason I upgraded from it was the aging graphics chip it used. I figured a Thunderbolt 3 port would allow me to upgrade the graphics chips down the road, extending the life of the laptop.

At work, to support our Mac users, I use a 2016 MacBook Pro with 4 Thunderbolt 3 ports.

This year, we decided that new laptops acquired for staff should also include Thunderbolt 3, and that we could start looking for a universal docking station for use with any laptop going forward. We ordered a Dell Latitude 5480, which reviews showed as having a Thunderbolt 3 port.

Things were looking promising for Thunderbolt 3; the one port to rule them all.

And then...

I recently acquired a Gigabyte Aorus GTX 1080 eGPU (external graphics) box. Graphics cards are extremely expensive due to the cryptocurrency mining craze, but somehow the Gigabyte eGPU managed to be the cheapest GTX 1080 available. While researching eGPU configurations for my Asus laptop, I discovered that the Thunderbolt 3 chip Asus used was an "LP" version that only worked at 20Gbps (half of Thunderbolt 3's advertised peak speed). Asus does not list this anywhere on the product page, and this chip is essentially Intel's dirty little Thunderbolt 3 secret.

Next, our order for the Dell Latitude 5480 came in, along with the Thunderbolt 3 docks. I connected the dock to the Dell and discovered that only a specific configuration of the 5480 (with a completely unrelated GeForce 930MX graphics chip) includes Thunderbolt 3. The model we received has a regular USB Type-C port. Fortunately we were able to return the laptops and order replacements with the Thunderbolt 3 port, but Dell is needlessly creating confusion on this laptop. If you've been considering it, be careful ordering.

Finally, I connected the Dell Thunderbolt 3 dock to the 2016 MacBook Pro. Nothing. Apple has a "whitelist" of supported Thunderbolt 3 devices, and unsupported devices simply won't work. There is a hack that removes Apple's arbitrary and artificial device check. Once I went through those steps, the dock functioned mostly OK; everything worked but only one external display can be used.


Perhaps there is some hope for Thunderbolt 3. Intel is making Thunderbolt 3 royalty-free, so it may start showing up in more devices. I just hope that laptop manufacturers stop using the slower version of Intel's Thunderbolt 3 chip, or at least are more clear which chip they are using. Other Thunderbolt 3 docks are supported by Apple (though they are significantly more expensive of course), and offer Windows compatibility as well. Although I could say I hope that Apple removes their ridiculous "supported" check, Apple's history makes that scenario unlikely.