From owner-freebsd-smp Thu Jul 24 14:01:34 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id OAA23832 for smp-outgoing; Thu, 24 Jul 1997 14:01:34 -0700 (PDT) Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.50]) by hub.freebsd.org (8.8.5/8.8.5) with SMTP id OAA23822 for ; Thu, 24 Jul 1997 14:01:28 -0700 (PDT) Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id NAA18060; Thu, 24 Jul 1997 13:57:17 -0700 From: Terry Lambert Message-Id: <199707242057.NAA18060@phaeton.artisoft.com> Subject: Re: Lots 'o PCI slots To: lamaster@george.arc.nasa.gov Date: Thu, 24 Jul 1997 13:57:17 -0700 (MST) Cc: freebsd-smp@FreeBSD.ORG In-Reply-To: <199707242002.NAA24606@george.arc.nasa.gov> from "lamaster@george.arc.nasa.gov" at Jul 24, 97 01:02:19 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-smp@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > That could be welcome news in some cases, but, since Unix/BSD folks > tend to shy away from such boards anyway whenever possible, it seems > that the only real "benefit" for well-behaved boards is going to be > increased latency. For example, the most performance-critical > path is usually the SCSI controller. If the controller already > has a minimal-interrupt message-passing flavor, does gather-scatter, > etc., what's the difference? Except for the added PCI bus traffic > and the added latency due to the I/O request having to get processed > in the I2O processor. > > What am I missing? PCI-PCI bridging, I would guess, where the i960 is a cluster communications processor more than simply a method of offloading interrupts. It would be a relatively cheap method of obtaining background distributed cache coherency processing (among other things). One might even use the i960 for the scheduler and for forcible process migration. Only a theory... Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.