Date: Tue, 15 Jan 2002 17:50:45 -0800 From: Ulf Zimmermann <ulf@Alameda.net> To: hackers@freebsd.org Subject: USB UHCI speed issue ? Message-ID: <20020115175045.Y98001@seven.alameda.net>
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I am looking at libnjb (Library to talk to a Creative Nomad player).
From the README:
It appears that the uhci device under FreeBSD performs poorly on
bulk data transfers. The USB 1.1 specification defines 1000 "frames"
every second, for 1 frame per ms. The host controller determines
how many packets to place in each frame, based on available bandwidth
and bandwidth requirements. This is called "bandwidth reclaimation",
and the FreeBSD USB stack does not do this as of 4.4-RELEASE. The
end result is only one packet sent per frame, which severely limits
the transfer rate: the NJB uses 64-byte packets, and the math gives
us a data transfer rate of 64,000 bytes/second. Yuck.
If you have a UHCI USB controller, this will bite you. If you have
an OHCI USB controller, the ohci device driver "does the right
thing", and will give you 430kb/second (or so). However, there is
a caveat: I have noticed some instabilities in the ohci driver, so
you may have problems here, too.
This problem with the uhci stack has been fixed under NetBSD, but
this new code has not yet been ported to FreeBSD.
Has this been fixed in -CURRENT ? And if so, can someone point me
at what files I can try to get onto -STABLE to get a higher speed
out ? I am working on an application and 64,000/sec is slow to test
things.
--
Regards, Ulf.
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Ulf Zimmermann, 1525 Pacific Ave., Alameda, CA-94501, #: 510-865-0204
You can find my resume at: http://seven.Alameda.net/~ulf/resume.html
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