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List:       linux-usb-users
Subject:    Re: [Linux-usb-users] Problems with Maxtor Personal External USB HD
From:       Alan Stern <stern () rowland ! harvard ! edu>
Date:       2005-11-21 20:21:35
Message-ID: Pine.LNX.4.44L0.0511211511340.4586-100000 () iolanthe ! rowland ! org
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On Tue, 22 Nov 2005, Matthew Donaldson wrote:

> Quoting Alan Stern <stern@rowland.harvard.edu>:
> [...]
> > It could be a problem with your EHCI controller, your cables, or your
> > drive (the fact that it works at full speed doesn't mean it will work at
> > high speed).  Have you tried plugging the drive into a different computer
> > to make sure that it is okay?  Have you tried plugging a different
> > high-speed device into your computer?
> >
> > In the end you may need to do what I said before: get an add-on PCI USB
> > controller card.
> 
> Ok, I'm planning to test it out on another machine today.  Getting a PCI card
> isn't such an easy option as I don't have any PCI slots free.

Sometimes just adding a USB 2.0 hub between the computer and the drive
will improve things.  I'm not sure this strategy will help in your case,
though.  It depends on the exact nature of the problem, which we don't 
know.

>  Just out of
> interest: I don't hear of Windows users having to go off and get PCI USB cards
> to make things work.

I don't hear about it either, but on the other hand, I don't hear about 
Windows hardware problems much at all -- and certainly there must be 
plenty of them!

>  Does this sort of thing tend to be a true hardware
> problem, or is it just that Linux support for some EHCI controllers 
> isn't fully
> there yet?

I really don't know.  I have seen examples of systems (not with the same
hardware as you) where Linux wouldn't work but Windows running on the same
computer would.  Is this because the Windows drivers include specialized
quirk handling?  Is it because Linux pushes the hardware harder and not
all the hardware is able to cope?  Is it because manufacturers test their
products under Windows but not under Linux?

Beats me.  As far as I know, the only remaining problems in the Linux 
ehci-hcd driver involve scheduling of periodic transfers, particularly 
when using a transaction translator.  None of that comes into play when 
talking to a disk drive.

Alan Stern



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