On Thu, 6 Oct 2005, Steve Calfee wrote: > >One last question on this thread for those that know the drivers and the > >hardware. What is the best explanation for the fact that the low > >quality cable works flawlessly with the uhci-hcd driver and the same > >hardware. Obviously the data transfers run at a slower rate, however > >the ehci_hcd driver won't even negotiate a connection. If you don't > >have the time to answer this don't bother, I am just curious. > > > >Thanks for your time. > > > >Jon > > > > I cannot give a good answer because it depends on so many things. If you > imagine a manufacturer making the lowest possible cost cable that just > barely works on "full speed" it is not too much of a leap to suppose that > that cable will not run at 40 times that barely working speed. 480 Mhz is no > slow speed, when you consider that most ethernet runs a 100Mhz, and we have > all had marginal cables for that too.
Another thing to keep in mind is that all cables distort the signals passing through them to some extent: stretching the pulses, adding random noise, echos, and other things. When the pulses are 1/12 us long (full speed) they can withstand a fair amount of stretching and other distortion. When they are only 1/480 us long (high speed) they can't. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: Power Architecture Resource Center: Free content, downloads, discussions, and more. http://solutions.newsforge.com/ibmarch.tmpl _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
