Disable EHCI or Forcing Full Speed to High Speed Hub

[turbodude]

Hi all, I work for a company that supplies systems that use a number of Full Speed PIC micro based boards plugged into a number of cascaded High Speed USB hubs (DLink DUB-H7). A typical system would have 3 hubs connected (cascaded) to a single USB port on the PC (WinXP & soon Win7) with 5 or more full speed micro boards distributed across the 3 hubs. Cables are 5meters between each hub. We are forcing the whole system to run at full speed because there were enumeration and dropout issues under high speed. Depending on the version of motherboard we either do it by disabling EHCI's in device manager or in the BIOS (therefore it defaults to using the UHCI = full speed). This has been working fine.

We are now assessing a new PC based on the Z68 intel motherboard chipset for suitability and this does not seem to have a UHCI so we can't disable the EHCI to force full speed.

Is there any other way to force full speed comms from the PC in this situation when all hubs are USB2.0 High speed?
Obviously we are working on getting the system stable under high speed but I need some time.

For example is there any specific chipset PCI/USB card that may be suitable?

I am open to absolutely ANY suggestions that may buy us some time.

ps: Jan, I bought your USB Complete Book which has been excellent in helping my understanding of USB in general.

[Jan Axelson]

Use 1.1 hubs? Belkin says this is a 1.1 hub:

http://www.belkin.com/IWCatProductPage.process?Product_Id=367655

Hard to believe these would be on the market now, but as the manufacturer, Belkin should know. It doesn't seem to have a power supply and thus can supply only 100 mA per port.

Of course there must be plenty of "vintage" 1.1 hubs lying around in everyone's closets.

I'm glad to hear you found USB complete useful.

Jan

[turbodude]

Thanks for the quick response Jan. Sourcing a large supply of USB1.1 hubs that are USB-IF approved seems to be very difficult (including the one you linked to). We are still trying as a backup plan.

To help anyone else that has the same issue I will mention that we are currently(since I posted this thread) having some success in testing an NEC D720101 based PCI/USB2.0 card that does indeed allow us to disable the EHCI and run just on its OHCI which effectively disables High Speed.

We also tried USB3.0/PCIe cards which are based on a different NEC chip and they have a single xHCI so there is no way to force full speed with them.

Thanks again.

[Jan Axelson]

Of course the solution is to fix the device so it runs at high speed even with multiple devices and hubs. You shouldn't have to work around a defective device by forcing a slower speed.

Jan

[turbodude]

Yep, agree totally. That's why my first post said "Obviously we are working on getting the system stable under high speed but I need some time."