> > To all: I just checked the device manager and found 16 USB > controllers. Eight of these were USB root hubs. I disabled 4 of > these and DLC value went from 950 microseconds to 30 > microseconds. For those with drop out problems, I would start at the > USB folder in your device manager and see how many you can live > with. Dale KC2PZ >
Neal's advice to look at the IRQ sharing carefully is good advice. In terms of USB: The USB controller story is confusing, and I'd suggest folks not "go there" by default. Here's why you see so many USB controllers on a system: Remember that we have USB V2.0 (supporting High Speed) that's backwards compatible to USB V1.0 and V1.1 (supporting Low Speed and Full Speed). They way they get this backwards compatibility is pretty strange. USB V2 controllers are EHCI controllers -- You'll see them listed as "USB2 Enhanced Host Controller" in device manager. Every EHCI controller has built into it 4 (count em) UHCI or OHCI controllers. These controllers handle backwards compatibility (low-speed and full-speed devices), and appear to Windows as entirely separate devices. Because, they ARE (effectively) entirely separate devices. In addition, each of these controllers has an associated Root Hub. That's what provides the on-board USB sockets to plug into. So, with just one USB V2.0 controller you get: 1 USB V2.0 High Speed controller (EHCI) 4 USB Low Speed / Full Speed controllers (OHCI or UHCI) 5 Root Hubs Disable the EHCI controller, and you won't have any more support for High Speed. Disable one of the root hubs, the built-in USB ports on your machine will stop working. The moral of the story: Feel free to disable stuff. Now at least I hope you have a better idea of what you're disabling. Just wait until we have USB V3.0 (USB Super Speed) to deal with. Oh, that'll be a treat. Peter OSR _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
