On Friday 27 February 2004 02:32 pm, John Richard Smith wrote: > >You should be able to look at your motherboard manual and it will tell you > >exactly where the 2.0 sockets should be connected on the motherboard. > > Follow that plug to the external socket and plug your device in there. > > OK, but the manual isn't clear ,it merely says US2 compatible without > saying which slots.
Always the possibility that they are all 2 compatible but the presence of certain devices is forcing them down to 1.1. With backwards compatibility, there is no real reason, short of cost, for anyone to install a purely 1.1 usb controller anymore. > According to kde, > RISER BOARD > slot1 = USB2/480MB/sec , Scanner > slot2 = USB1/12MB/sec , Printer(UHCI? or OHCI? doesn't say) > slot3 = USB1/OHCI/12MB/sec, Camera > slot4 = empty > > MOBO > slot1 = USB1.12/UHCI/12MB/sec, > slot2 = empty > > So from what you are saying then, the riser board are all USB2 slots, > but since some of the devices, > namely printer and camera, are not usb2 compatible, they get set up as > USB1 and OHCI or UHCI > The Mobo slots are both USB1 and UHCI but could be OHCI ? That could very well be. All of your USB ports may be 2.0 compatible but the act of plugging in any 1.1 device will server to lower the hub down to 1.1 in order to maintain compatibility with the device. At least, that is my understanding of how USB works. > I suppose the way I have it above it's a waste of an USB2 slot to plug a > USB1 device in it, > if, as in my case, I have a spare USB1/mobo slot. > So what really determins whether a USB1device is UHCI or OHCI ? "What is the difference between OHCI and UHCI controllers? In brief: OHCI is made by Microsoft and emphasizes the fact that hardware should be smart to facilitate the software's task. UHCI is made by Intel and stupid, in order to facilitate a low gate count. Bottom line, OHCI has some brains and is actually able to transfer 8kb transfers in one go. UHCI needs to be told every single thing about a transfer: transfer descriptors, size of transfers, but also the sequence in which iso, interrupt, bulk and control transfers need to be done. It also means that the amount of overhead on the PCI bus on OHCI should be lower, allthough I have not measured that yet. OHCI is being used in firewire as well I believe. UHCI is simply to slow for that." Hardware manufacturers build both standards onto the MOBO just in case you have a device that is particular. If the device supports both, it probably registers a preference for one over the other and thus gets assigned to that controller. -- Bryan Phinney Software Test Engineer
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