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USB 4 vs Thunderbolt

pderbidge

Senior Member
I would love if someone had some real insight to how this is going to play out with Audio Interface manufacturers. From what I understand, USB4 will support the Thunderbolt standard. Does that mean that existing Thunderbolt products will work with USB 4 or will there have to be new interfaces made to support it? If new devices have to be made then my question is are manufacturers planning to do just that. What I found disappointing with USB 3 is that even though theoretically it was faster than Firewire, in practice (due to technical differences between the way USB3 worked vs Firewire) it seemed that firewire still outperformed USB3 in Latency tests so the consensus among manufacturers was to keep making USB2 drivers because there was no advantage to USB3. I'm hoping that USB4 changes this and we can start seeing lower latency audio interfaces like we do with Thunderbolt and PCIe.
 

colony nofi

Senior Member
Unfortunately this is a much trickier topic than a simple forum post is going to answer.

Between these 3 articles, you should be able to get your head around what we *expect* from USB4 (as the official documentation papers have not yet been released, so things can and will definitely change!) The verge article in particular makes a few issues (and things we don't know) quite clear.



So - for audio - what does this mean?

1. The connector is going to remain USB-C. I think all and sundry breathed a sigh of relief on hearing that.

2. USB4 is going to be able to handle TB4 (EDIT : TB3) as well as USB4 type data streams. See - we're already getting confusing. (USB3.2 was / is hard enough!) Among other data and power transport streams.

See, USB4 is a data transport stream in its own right (running at the same speed as Thunderbolt 3 - 40Gb/s - but NOT thunderbolt 3. AND a connection standard using USB-C cables that allows a bunch of different data streams. (This is already confusing right? At least it will be better than the current gen!)

I would assume that people will keep calling "thunderbolt" audio interfaces exactly that, and usb4 interfaces exactly that. Now, it remains to be seen what the USB4 spec will actually mean for interface manufacturers. Will it be cheaper than TB3 to implement (doubtful at the start at least) and will it be better (again, doubtful.) The bandwidth will be identical, but USB is a slightly different animal in regards to the way it interacts with the rest of the computer. Very early conversations I've had see people skeptical that it would do any better for latency than a well designed TB2 or 3 interface would.

Remember - data all moves at a set speed. Its the width of the pipe that changes. So once you have a pipe that can handle all the audio data you need (which USB2 does for the most part) then it becomes about implementation, not bandwidth. (Ok, so thats a simplification, but its the spirit of the argument I'm after)

Latency is in its own way an interesting animal. Some well designed USB2 interfaces offer better round trip latency than poorly implemented TB1/2/3 (I use the word "poorly" word carefully, as there are so many decisions involved in why a certain implementation is decided upon that one can't really say an idea is "poor" - more than the considerations were different to the ones we'd like the manufacturer to take into account...)

Now to answer just a few of your questions.
We do know that USB 4 will work with TB3 devices. And as far as I'm aware TB2/1 devices. (I have yet to have a TB2 or 1 device I cannot run over TB3. You just need to use a convertor which are not cheap)

We do not know for sure that all previous USB 3.x or 2 or 1 will work with USB4. And because the standard isn't locked down, there's more than a fair chance that some manufacturers will just go ahead and mess with the spec anyway, so it won't be a case of EVERYTHING working but just MOST or SOME. A crapshot for consumers (kinda like the issues with cables using the USB-C connector... damn it we NEED some sort of colour code / design to let us know if they're charging only cables, USB2 speed, USB3 or 3.1 speed, can carry TB3 (ok, so that one is sorted with the lightning bolt symbol) etc etc.
 
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