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> the core problem here (lack of USB2 on a USB3 connector) Not sure if that's the core issue here? That's one of the issues, but there are more uses for that c
by MayeulC 5y ago
> the core problem here (lack of USB2 on a USB3 connector)
Not sure if that's the core issue here? That's one of the issues, but there are more uses for that chip, like the introduction that hints at sharing USB3 bandwidth between multiple USB2 devices.
- dsr_ 5y agoYeah, this. A person not familiar with this situation would think that if a USB3 hub had USB2 ports on it, it would do packet level buffering and switching so that the 5-10Gb/s of the USB3 upstream would be shared among the 480Mb/s USB2 ports. It should be reasonable to get 8-10 USB2 ports all operating at their maximum bandwidth off of 1 USB3 port. After all, that's how Ethernet works.
- marcan_42 5y agoAnd the reason why that doesn't and can't work with USB2 is because, unlike Ethernet, USB is extremely closely tied to its physical layer and you cannot actually buffer and switch USB packets at all (without cooperation from at least one side). All communications are host-driven and stateful, and the timeouts for replies are on the order of single-digit microseconds, and the receiving end has no obligation to accept data, so there is no way to safely buffer data and forward it at a later time because that time might never come, and the mere act of accepting data from one end desyncs both ends' ideas of what data was successfully transferred, which can have higher level protocol implications. USB is a clusterfuck of a standard.