From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <56cf6b7b6176d2a7d381d7d8d91e1896@proxima.alt.za>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] TODO lists for Plan 9
Date: Fri,  9 Jul 2004 12:34:20 +0200
From: lucio@proxima.alt.za
In-Reply-To: <1afc3ca5d80c7130d54cdd41d9805836@collyer.net>
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Topicbox-Message-UUID: bb0585c0-eacd-11e9-9e20-41e7f4b1d025

> I think OHCI and UHCI were competing USB 1 interfaces.  One was from
> Intel and appears on lots of motherboards; I'm guessing that that's
> UHCI, since that's what Plan 9 currently supports.  EHCI must be the
> USB 2 interface I was thinking of.

I'm sure there are others whose knowledge is greater than mine, but
they must be asleep as no one has shouted at me yet :-)

I have both UHCI and OHCI specs (and EHCI, believe or not).  I haven't
yet been able to read both (either, really, I only superficially read
the UHCI one) and so I don't know how they differ: Universal (Intel)
and Open (Compaq, of all names, but all USB designers at the time seem
to have had a hand in this one).  I have a feeling that OHCI has
superseded UHCI in practice, possibly because of its appearance in all
EHCI implementations.  But I'm guessing and my experience is not very
broad.

As for EHCI, by volume the specification does not seem much greater
than OHCI, but I'm sure there lurks some serious complication
somewhere in its innards.

++L