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two questions: why USB2 instead of USB3 and will there be a multi-nic version at some point?

e14 Contributor

Why is the PI using USB2 instead of USB3 at this point and is there any plan to come out with a multi-nic version of the card?  I can see this being used as a very nice little firewall if one could stack, say, 3 nics on the card.

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  • One of the design targets for USB 1 was that "standard" chips could drive it. That's why you see software implementations of USB on Atmel ATMEGA8 chips and things like that. The lowest level hardware interface would work at 12Mbps, but then the software wouldn't be able to keep up. But if you design a chip USB1.1 is easy on the hardware level. (the protocols are kind of complicated).

     

    Next there is USB2.0, the "high speed, 480mpbs" variant. This requires slightly special drivers, lower voltages for the core electronics, but with modern processors running 500MHz+ this isn't much of a problem. This is what the broadcom has.

     

    Now upgrading from there to USB3.0 means that the stuff is much more difficult to integrate in an existing chip design. Many chips are either specific USB3.0 chips, or they need a special driver chip. In short not something that is easily bolted onto the broadcom chip that powers the 'rpi.

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  • One of the design targets for USB 1 was that "standard" chips could drive it. That's why you see software implementations of USB on Atmel ATMEGA8 chips and things like that. The lowest level hardware interface would work at 12Mbps, but then the software wouldn't be able to keep up. But if you design a chip USB1.1 is easy on the hardware level. (the protocols are kind of complicated).

     

    Next there is USB2.0, the "high speed, 480mpbs" variant. This requires slightly special drivers, lower voltages for the core electronics, but with modern processors running 500MHz+ this isn't much of a problem. This is what the broadcom has.

     

    Now upgrading from there to USB3.0 means that the stuff is much more difficult to integrate in an existing chip design. Many chips are either specific USB3.0 chips, or they need a special driver chip. In short not something that is easily bolted onto the broadcom chip that powers the 'rpi.

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