eli5 What is thunderbolt 4? what’s the purpose of thunderbolt cables?


eli5 What is thunderbolt 4? what’s the purpose of thunderbolt cables?

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There are port standards. Like HDMI 2.0, USB A 3.0, Lightning etc. they dictate things like how much power, data or display so that there is some form of standards between devices since they need to connect to others.

Thunderbolt 4 is one of those standards. Thunderbolt is physically similar to USB-C but thunderbolt has higher amounts of data, display, and power connectivity than standard USB-C.
Normally thunderbolt 3 already has double the data speed and higher display capability, but thunderbolt 4 goes further than that with higher display specs.

The perephreal standards are usually broken into multiple different parts. You have one standard for the physical connector, pins and wire. One standard for the way data is encoded into these serial busses. And another standard for what signals to send, which protocol to use. This have become quite confusing for people as different standards chose to use the same physical sections or the same protocol.

Thunderbolt can use either DisplayPort or PCIe as a protocol but using seperate cables and connectors as well as management traffic to negotiate which protocol to use. It allows you to connect various PCIe devices such as network cards, graphics cards, NVMe drives, etc. to a laptop through a single cable, perfect for docking stations. It also allow you to daisy chain DisplayPort monitors together so they only use one Thunderbolt connector in your laptop.

USB on the other hand use a seperate protocol so it is harder to use any PCIe device without an active adapter. For example an NVMe drive can connect physically directly into a Thunderbolt connector with only a tiny chip to handle the management traffic while the same NVMe drive need a fast chip to convert the signal into a USB mass storage device signal or a PCIe over USB signal to use over USB. Notice how USB adapters for things tends to be more expensive then Thunderbolt adapters, with some exceptions of course. But this does mean that USB can use cheap hubs so you can connect various different USB devices to the same laptop. This is unlike the daily chaining of Thunderbolt devices.

Thunderbolt 3 can use USB-C connectors and USB 3 cables. Even the serial signal inside them is the same so there are plenty of hardware which can detect if you have connected a USB device or a Thunderbolt device into the same port. However people are experiencing difficulties when trying to use their Thunderbolt 3 devices as a USB hub. The protocols just does not work that way and there is no way to address the devices. You get strange issues such as being able to connect one monitor into your docking port but when you connect the next it does not work for some reason.

This is what Thunderbolt 4 fixes. They have now added the ability to connect devices in a hub and spoke network. This have takes quite some work. They have had to redo how they address devices and packets, how they merge different data streams from different sources into a single wire, etc. So while the speed have not improved it have become more usable with less problems.

There are different types of connectors. An HDMI port looks different from a toslink port which looks different from a USB-A port which looks different from a micro-USB port.

Thunderbolt uses a USB-C connection, so it looks identical to any USB-C cable. Thunderbolt specifically though can carry more data, something like 2x that of a normal USB-C cable, and likely different support for external monitors.

If you get a cable rated for Thunderbolt 3/4, it will work for USB-C data purposes as well.

There are different types of USB-C cables as well. There are some that are for power/charging only. And sometimes a USB-C that can carry both power and data won’t work for only charging purposes. I have a USB-C chargeable LED video light, and my MacBook USB-C cable will not charge it.