The best USB explainer video I've seen

Have you sometimes wished you could understand modern USB? Not just the Full Speed / High Speed USB 1.0-2.0 crap, but all the fancy stuff added ever since? Like Thunderbolt, DisplayPort encapsulation, and PCIe over USB? Have you ever wondered why docks like CalDigit's TS4 and TS5 cost 400 euro and above?

I recently hit a jackpot while surfing the web, let me share it with you.

Required context

The video focuses on USB 3 and 4, so I recommend taking a quick look at:

USB hardware

The initial versions of the USB standard specified connectors that were easy to use and that would have high life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data links. All versions of USB specify cable properties. Version 3.x cables, marketed as SuperSpeed, added a data link; namely, in 2008, USB 3.0 added a full-duplex lane (two twisted pairs of wires for one differential signal of serial data per direction), and in 2014, the USB-C specification added a second full-duplex lane.

It's also worth knowing that USB communication begins with sending advertisements and negotiating common values for speed, supported features, and (in case of USB-PD) voltage and power draw.

Also, nowadays, the cable is often more than just some wires. It has its own microcontroller that sends its own advertisement.

The subject in question

Without further ado, here's the video. Enjoy!

The key surprises

DisplayPort can be transferred through Alt Mode (some physical pins are used exclusively for DP) or encapsulated (in-band with USB traffic, packet routing happens inside the dock). The former is why monitors with builtin hubs let you pick between 3840x2160@60.00+USB2.0 (2 pins dedicated to DP) and 3840x2160@30.00+USB 3.0 (4 pins dedicated to DP), while you don't need to make such tradeoffs with nicer docks. But decapsulation requires expensive silicon.

Despite USB4 and TB5 being "the same" technology, Thunderbolt logo is a sign of all features being supported, while USB standard leaves some optional.

What does it mean to officially be a Thunderbolt device? That depends if you are a host (PC/laptop), a hub, or a peripheral.

USB4 has done away with all connectors but Type C, and all confusing terms like "Gen2 2x2".

USB4 is making Power Delivery support mandatory. Amazing! Does it mean no more surprises with 5W / 10W charging?

The maximum length for cables keeps going down. We're looking at 1m passive cables, or 2m active (read: expensive) cables, or crazy expensive optical cables. Plan your desk setups wisely.

Bonus

Since the video was published, we got USB4 2.0 and TB5. At first glance seem like same things as before, just faster. But! They now support asymmetric speeds! So you can sacrifice some hub->host speed for faster host->hub (i.e. more displays). That's pretty cool. See:

What is Thunderbolt 5 Bandwidth Boost?

One of the major advertised features of Thunderbolt 5 is something Intel calls “Bandwidth Boost”. Thunderbolt 5 is capable of up to 80Gbps bi-directional b

Bonus 2

If you want to spend your money on TB5 cables, it seems like you have options between CalDigit, StarTech, UGreen, Anker, Belkin, Cabble Matters, OWC, Plugable, or Apple. LinusTechTips' cables are TB4 only.