USB Speeds Are Fake (But NOT Why You Think)

I should probably clarify the distinction in my criticisms between what you might call the "line encoding overhead" vs "regular overhead" (Not official terms but you know what I mean). My main criticism about the naming scheme is only with the difference between: 1 The advertised speed (such as 5 Gbps), and 2 The raw signaling rate minus line encoding overhead (which would be 4 Gbps in the case of the 5 Gbps rating). And I criticize only this difference specifically because the line encoding overhead is constant and and could be accounted for if they wanted, like has been done with network speed ratings. Then there is also the "regular overhead". And while I of course still wanted to talk about that in order to explain the rest of the difference, my criticisms do not extend to accounting for the regular overhead in the naming scheme. I probably should have used a better word than "misleading" at 6:39, because while I'd say it's linguistically true, I think it wrongly implies fault by the USB-IF in not accounting for the entire 12% difference, while really only 3% is because of the line encoding overhead, and the rest is regular overhead. Probably "confusing" would make more sense. But again I more meant to describe the regular overhead difference in a purely informative sense.

Thank you for providing English subtitles. They are very important for YouTube to be able to translate correctly. For example, I speak Portuguese. YouTube's speech recognition doesn't generate very good subtitles in real time and the translation in this case is even worse. I'm always very happy when there are native English subtitles. As for the video, wonderful, I had no idea about all this USB confusion. 😅 Greetings from Brazil. 👏🇧🇷

It's good that the USB branding all around is so consistent and never misleading😎👌

8b/10b is actually amazing. For the extra data you get parity, DC balance, PLL synchronization, and out of band control characters. Simply amazing. 128/132 will most likely be well behaved but it is not guaranteed. Don't knock encoding schemes unless you know what problems they are trying to solve. Yup, electrical engineer here.

If I remember correctly, the reason that networking speeds are reported as actual speeds is a legal reason because in some countries including the US, if I'm remembering correctly, networking is mandated to deliver within something like 2% of advertised

Bandwidth sharing is a major issue people come up against. Dedicated USB channels are expensive to produce, so a lot of motherboards share bandwidth instead of providing dedicated ports. It's why there's such price disparity with PCI-e USB cards, where some that have more ports are cheaper than those that have less ports but don't share bandwidth across each port.

You can't ignore flow control, framing, error correction and protocol overheads from one but count them all against another. PCIe 3.0 and later still have all of those overheads in addition to line encoding overhead, so the practical througput is only around 80% of the line rate. This means a PCIe 5.0 SSD won't get much faster than 100Gbps despite having a 4·32Gbps or 128Gbps connection. Even the TCP/IP commonly used with ethernet is only 94% efficient with the default packet size while 10GbE and faster can overwhelm less powerful systems. Ethernet routers and switches can also be limited by the total packet per second throughout, so very many small packets won't make full use of the link rate

I really enjoy your content and the way you deliver it. Excellent balance between not too noob and not too expert. As an IT support person, i am still learning stuff every other videos and I thank you for that.

Super informative. And yeah, USB 2.0 equals 35 MB/s max. is what you see in practice. There are so many stupid ports, cables, adapters and enclosures which bottleneck your chain to 2.0 that I'm still painfully aware. Getting a full setup from Mainboard to drive with 3.1 speeds is a challenge.

A good clear explanation of the difference between signalling speed vs data speed. Excellent video.

That was a seamless transition to the sponsor. Well done!

Love your explanation of every person in you audience and no wonder everyone loves you, almost there is always a few out there that I don't understand.

very informative, thank you for your efforts enlightening the people to be informed in this very dynamic yet standard tier of tech knowledge! Not only that, the clear explanation as to why this topic is as is, much appreciated

Thanks for the video, very informative 🙂

I'm pretty sure that I've read that the newest version of USB-C is 80/80 Gbit by default and the 120/40 configuration is meant for video signaling. I could be remembering wrong, though. Either way, I doubt we'll see anything use that in some time. Thunderbolt 80Gb meanwhile could be very useful for external GPUs.

Of course USBs wouldn't be at the speed of light 😂😂😂

Great review, I've watched it a few times and always go back for reference. Could you please let me know the maker/link of your cable tester to check is the resistor is present in a USB-C/USB-A cable? Thanks

I want to add another thing, the reason 8b/810 is done is because at the end of the data transmission (or while) the amount of zeroes and ones that pass through must to 50/50, if there are 10000 ones in a transmission, there MUST be 10000 zeroes in it.

my 10 dollar USB claiming to have 500Gb per second and 1 petabyte of storage

Absolute unit of a thumbs up 👍🏻