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Comment by mdaniel | Hacker News Reader

And then there's the madness that is the physical USB-C plug which is sometimes also Thunderbolt over the same connector: https://www.intel.com/content/www/us/en/architecture-and-tec... along with sometimes DisplayPort and/or HDMI: https://en.wikipedia.org/wiki/USB-C#Alternate_Mode_partner_s...

I will presumably forever be mystified why I can only get "fast charging" on my Pixel 4a with USB-C-to-USB-C into the Google power brick, and never USB-A-to-USB-C into any power brick labeled as "fast charge"

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> USB-C-to-USB-C into the Google power brick

This is USB Power Delivery (USB-PD for short). It is exclusive to the USB Type-C connector, and will work with any Type-C, PD-compatible charging brick. Bricks with various wattages are available (e.g. for charging PD-compatible laptops as well as phones).

> USB-A-to-USB-C into any power brick labeled as "fast charge"

This is legacy fast charging via any of a myriad of proprietary FC standards (Qualcomm QC, Samsung AFC, Apple 2.4A, etc., etc.) Since your Pixel does not support any proprietary fast charging standards, it will not work.

USB-PD is not exclusive to the USB-C connector. USB-PD rev. 1 was finalized in 2012, whereas USB-C 1.0 was finalized in 2014.

This is technically correct but AFAIK USB-PD 1.0 saw essentially zero adoption.

Power Delivery ("PD") requires chips inside the cable's connectors to work. The chips provide information on the cable's capabilities. No chip, then standard voltage, standard current only.

Thunderbolt is 40 Gbit/s over two serial lanes. That's 20 billion bits per second over a single link. I'm not an expert in this field (i.e., the field of high-throughput cables) at all, but that doesn't sound very realistic to me for regular cabling. But I guess the use of copper, gold contacts(?), differential signaling, shortness of the cable (or alternatively active components), and an immense amount of shielding make it possible. These cables are quite expensive.

The cable ID is only required for the higher end of possible currents. You can still get 60W (20V, 3A) through a non e-marked cable with USB-PD, just not 100W (20V, 5A).

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