USB Cheat Sheet

USB 4.2 (later renamed to USB 3.2 gen 2 Mk. 1) comes with built in time traveling. They just keep adding features to the protocol and making it complicated.

Re: USB Cheat Sheet

#8

Post by legalcorrection » Thu, May 05, 2022, 10:10 AM UTC

Suggestion: maybe include all the USB-C-plug Thunderbolt versions too. My personal policy these days is to just buy reputable Thunderbolt cables for all my USB-C needs. Maybe I'm doing the wrong thing?

Also, I think there's a difference between active and passive USB-C cables, or something like that.

Re: USB Cheat Sheet

#9

Post by johnwalkr » Thu, May 05, 2022, 10:11 AM UTC

willis936 wrote: post #4

a3w wrote: post #2

USB 4 (opt) is ... optical? Or optional?

It would have a longer max length if the data lanes were optical.

You can actually get optical usb3 and thunderbolt (all generations) cables. Thunderbolt was originally called light peak and shown off by Intel and Apple in demos as optical, and Sony had a line of laptops with optical light peak connectors to connect to external GPUs. But ultimately the default became non-optical because it can carry power too.

Re: USB Cheat Sheet

#10

Post by masklinn » Thu, May 05, 2022, 10:12 AM UTC

Some of the entries seem incorrect: "USB 3.2 (USB 3.2 Gen 2x2) and "USB 4" (USB 4 USB4 Gen 2×2) should have the same nominal data rate of 2500MB/s, they're 2 lanes (x2) of 10GB/s. Though they are apparently coded differently electrically, so they're distinct protocols.

The tables would benefit from mentioning the coding (8/10 or 128/132) as IMO it's one of the most confusing bits when you see the effective data rates:

* USB 3.2 Gen 1x2 has a nominal data rate of 10G (2 lanes at 5G) with a raw throughput of 1GB/s (effective data rates topping out around 900MB/s)

* USB 3.2 Gen 2x1 has the same nominal data rate of 10G (1 lane at 10G) but a raw throughput of 1.2GB/s (and effective data rates topping out around 1.1GB/s)

The difference is that Gen 1x uses the "legacy" 8/10 encoding, while Gen 2x uses the newer 128/132 encoding, and thus has a much lower overhead (around 3%, versus 20).