Date: Tue, 18 Feb 1997 06:21:58 -0400 (AST) From: The Hermit Hacker <scrappy@hub.org> To: David Greenman <dg@root.com> Cc: Jason Thorpe <thorpej@nas.nasa.gov>, Christoph Kukulies <kuku@gilberto.physik.rwth-aachen.de>, freebsd-hackers@freefall.freebsd.org Subject: Re: ccd and bounce buffers Message-ID: <Pine.BSF.3.95.970218062021.23132e-100000@thelab.hub.org> In-Reply-To: <199702180929.BAA04915@root.com>
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On Tue, 18 Feb 1997, David Greenman wrote: > >[ note, this reply is directed more at whomever integrated the ccd > > into freebsd, and/or has hacked on it in freebsd since then... ] > > > >On Mon, 17 Feb 1997 17:13:52 +0100 (MET) > > Christoph Kukulies <kuku@gilberto.physik.rwth-aachen.de> wrote: > > > > > Is it definite that ccd doesn't work for ISA (be it SCSI or IDE) > > > due to bounce buffers being required? > > > >So, maybe I'm missing how things work in the FreeBSD world, but what > >on earth does bounce buffers have to do with the ccd? The ccd is > >a layered driver, which knows nothing about the underlying component > >(or, at least, that's how it's _supposed_ to work, and is how it works > >in NetBSD). > > > >Really, any dependency on bounce buffers out side of specific scsi > >controller drivers is just plain broken. > > There is no dependency that I know of in FreeBSD. Bounce buffers are > handled in the generic SCSI layer (via a machine-independant callout), and > shouldn't be affected by ccd. I don't know where this rumor got started... > From personal experience, when I had tried to create a CCD device that spanned a PCI/NCR device and an ISA/Adaptec device, the machine would consitently "blow up" at boot with an error dealing with Bounce Buffers (this was months ago, so I don't recall the exact error message). Putting two PCI/NCR devices in (which she has now) runs beautifully.
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