I have an ECS 755-A2 motherboard (cheap Fry's special) that uses an SIS
chipset. Part of the chipset has a high speed (480Mbps) USB interface.
The high speed interface is handled by the ehci_hcd kernel module. The
low and full (12Mbps) speeds are handled by the ohci_hcd module.
It turns out that the high speed USB does not work with the ehci_hcd
driver. When the module loads, it gives all the indications that things
went properly, but when I connect a device (USB thumb drive) it fails to
go beyond a message that says a device was detected. No assignment of
/dev/sda1 etc. If I use the ohci_hcd driver only, I get proper operation.
Anyone else have this board? If so, does the USB 2.0 high speed work for
you?
Tested software is Knoppmyth R5B7, Knoppix 4.0.2 and Fedora Core 5. It
turns out the ehci_hcd module hasn't changed since Dec 2004 and is the
same in all these. Note that under Knoppix the ehci_hcd module does NOT
load by default; you have to modprobe manually. According to comments in
the module source code, the chipsets are supposed to have some sort of
standardized registers based on some reference design.
My workaround for now is to blacklist the module to prevent it from
loading. I edit the /etc/hotplug/blacklist file (on Knoppmyth; the
equivalent file on Fedora is /etc/modprobe.d/blacklist) and add ehci_hcd
at the end of the list. This prevents the hotplug system from loading
the module automagically. It also means I'm limited to full speed
(12Mbps) vice high speed (480Mbps).
Right now the BIOS has all the USB devices set to use EDB instead of PCI
for the bus. Knoppmyth won't even boot if I change it to PCI but Knoppix
and Fedora don't seem to care.
I've had this board for about six months but had never tested the USB
before so I don't know if this is an incompatibility problem or a
hardware failure.
Gus
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