Question Question about USB ports that never got answered in that article or comments

[Videogamer555]

I read over on https://www.tomshardware.com/news/usb-3-2-explained about all the different USB version names, and then there was an interesting comment in the comments section on that article that someone posted. I wanted to ask a followup question about that comment so I headed over to the associated forum page https://forums.tomshardware.com/thr...lained-whats-gen-1-gen-2-and-gen-2x2.3778787/ only to find that that page is locked from new posts. So I've started my own post here to ask the question.

Here's the question:
@Nikolay Mihaylov had commented that

All USB3+ connectors introduce separate data pins in addition to the USB2.0 data pins. A USB2.0 cable only makes contact with the legacy USB2.0 pins so everything works as if USB3 is not there at all.

Obviously, you want USB3+ for anything data intensive. Apart from the speed, it has the added advantage that it's full duplex, so data can flow simultaneously in both directions, like on Ethernet networks or PCIe.

BTW, 10Gbps USB3 introduces a new channel encoding which is more efficient. So while the 5Gbps variant translates to at most ~450MB/s real data (after accounting for channel encoding and protocol overhead), with 10Gbps you get ~1100MB/s. Consequently, Gen1x2 is slower (2x450 = 900MB/s) than Gen2x1 (1100MB/s). But it might work over longer distances.

I'd always assumed that the 5Gbps referred to the real data throughput rate (and it gets even higher when counting the overhead), as the real throughput is the only thing the average user cares about, so would be reported in the specs as such (nobody other than engineers cares about what the data rate is when also counting the overhead). Are you sure that for 5Gbps USB 3 the real data rate is actually only 450Mbps? 450Mbps is actually SLOWER than USB 2 (with a real data rate of 480Mbps).

Also you mentioned Gen1x2 in your comment. I've never heard of Gen1x2 before, and it wasn't even mentioned in the article you were commenting on. The only "x" mentioned anywhere in this article are Gen2x1 and Gen2x2. There's basically only 3 types of USB 3 ports: USB 3 Gen1, USB3 Gen2 (aka USB 3 Gen2x1), and USB 3 Gen2x2. I don't know where you got the idea of USB 3 Gen1x2 from. Can you please explain it?

And something else the article didn't really go into is the number of wires in the cable. USB 3.x cables have more wires in them than USB 2.x or 1.x cables. All USB cables before 3.x had only 4 wires. While older USB cables will work with older devices on USB 3 ports, USB 3 cables are needed to use USB 3 devices on USB 3 ports. This is because there's more than the standard 4 wires in a USB 3 device, cable, or port. But how many wires more? I know USB 3 Gen1 still had additional wires, but does USB 3 Gen2 have more wires than Gen1? Or does it use the same number of wires as Gen1 but the electronics just process data faster? How about Gen2x2? I know it has a different connector (USB-C) that has 2 sets of the same wires (to allow for reversing the cable), but if you ignore the duplicate wires, how many wires are used in Gen2x2? Is it the same as previous generations of USB 3? Or is it still more wires?

And just what exactly are the extra wires used for? Are they used to compliment the data on legacy wires (legacy wires used to send data in one direction, while new wires used to send data in the other direction) for full duplex? Or do USB 3 devices ignore the legacy wires, and do full duplex on the new wires only (are there enough new wires to actually do full duplex communications without also using the legacy wires)?

 

[Eximo]

Most of your answers are here:

https://en.wikipedia.org/wiki/USB

USB 3.2 Gen 1×2 is a thing, essentially USB is to blame for renaming USB so often.

Pins and wires would be equivalent from what you mentioned. I may be wrong, but I think all the pins in USB Type C are used (if implemented) in either orientation, they are just designed to be to used in either direction so that when you flip it, the same pin/wire is connected (they are mirrored essentially from top to bottom)

Power is a lot of the USB wiring today in addition to the extra RX/TX lines.