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[Bug 202022] slow (780KB/s) USB2.0 + VT82xxxx + yenta (cardbus pcmcia)



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Summary: slow (780KB/s) USB2.0 + VT82xxxx + yenta (cardbus pcmcia)


https://bugzilla.redhat.com/show_bug.cgi?id=202022


jreiser bitwagon com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Status Whiteboard| bzcl34nup                  |bzcl34nup
               Flag|                            |needinfo?




------- Additional Comments From jreiser bitwagon com  2008-04-04 19:55 EST -------
Please change 'Version' to 8; bugzilla won't let me.

The problem persists in Fedora 8 kernel-2.6.24.4-64.fc8.  A USB 2.0 flash device
reads only 641KB/s (327680000 bytes in 511.488 seconds; "time dd if=320MiB_file
bs=32k of=/dev/null")  The same hardware running with Cygwin on WindowsME reads
7.5MB/s (327680000 bytes in 45.248 seconds) which is more than ten times as
fast.  The device can accept write data at 3.3 MB/s under Fedora.  The device
definitely is a USB 2.0 device, at least /proc/bus/usb/devices has "Spd=480". 
Remember it is attached to a PCMCIA CardBus adapter that has 2x 256-bytes buffer
for USB2.0, and two USB1.1 controllers, each with one 256-byte buffer.  The
CardBus adapter also has a firewire (IEEE1354) device with a 2KB buffer. 
Speculation: somehow the driver is treating it as a USB1.1 device (limited to
12Mbit/s), or the 2 hardware buffers are not being used as a double buffer for
the purpose of sustaining continuous data transfer.

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