From owner-freebsd-hardware Sun Jan 5 19: 3: 1 2003 Delivered-To: freebsd-hardware@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0B07037B401; Sun, 5 Jan 2003 19:03:00 -0800 (PST) Received: from level.uwaterloo.ca (level.uwaterloo.ca [129.97.50.219]) by mx1.FreeBSD.org (Postfix) with ESMTP id 23C5C43E4A; Sun, 5 Jan 2003 19:02:59 -0800 (PST) (envelope-from bruce@engmail.uwaterloo.ca) Received: from level.uwaterloo.ca (localhost [127.0.0.1]) by level.uwaterloo.ca (8.12.3/8.12.3) with ESMTP id h0631R5n032633; Sun, 5 Jan 2003 22:01:27 -0500 (EST) (envelope-from bruce@engmail.uwaterloo.ca) Received: (from www@localhost) by level.uwaterloo.ca (8.12.3/8.12.3/Submit) id h0631Qm8032632; Sun, 5 Jan 2003 22:01:26 -0500 (EST) X-Authentication-Warning: level.uwaterloo.ca: www set sender to bruce@engmail.uwaterloo.ca using -f Received: from 65.93.103.72 ( [65.93.103.72]) as user bruce@engmail.uwaterloo.ca by www.nexusmail.uwaterloo.ca with HTTP; Sun, 5 Jan 2003 22:01:26 -0500 Message-ID: <1041822086.3e18f1868e32c@www.nexusmail.uwaterloo.ca> Date: Sun, 5 Jan 2003 22:01:26 -0500 From: Bruce Campbell To: freebsd-hardware@FreeBSD.ORG Cc: freebsd-questions@FreeBSD.ORG Subject: Re: ata "fallback to PIO mode" on dual processor AMD systems References: <1041368236.3e1204ac45da5@www.nexusmail.uwaterloo.ca> <025701c2b112$ddfbf580$1200a8c0@gsicomp.on.ca> <1041371397.3e121105cdf30@www.nexusmail.uwaterloo.ca> In-Reply-To: <1041371397.3e121105cdf30@www.nexusmail.uwaterloo.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit User-Agent: Internet Messaging Program (IMP) 3.1 / FreeBSD-4.6.2 X-Originating-IP: 65.93.103.72 Sender: owner-freebsd-hardware@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org Quoting Bruce Campbell : > Quoting Matthew Emmerton : > > > [ cc'ing Soren since he's the ATA guru ] > > > > > Dec 30 23:27:00 ecserv13 /kernel: ad0: trying fallback to PIO mode > > > Dec 30 23:27:00 ecserv13 /kernel: ata0: resetting devices .. done > > > > > > The test continues to run with the ata controller in PIO mode, with > > > slower performance, and higher load average. > > > > > > Once the master drops to PIO, attempts to access the slave then cause > > > it to drop to PIO. > > > > Are you using 80-conductor cables on all your drives? These are required > to > > get consistent high throughput, and running without them may cause the > > problems you're seeing. > > Thanks for the information about the design of IDE etc, and the suggestion > about the cables. I was about to shuffle things to get the disks > onto separate channels, but I now see that would be a mistake as my > CD drive would share a cable with a disk. ps. As an aside, I have since determined that putting a PIO device and a UDMA device on the same channel does not affect the performance of the UDMA device, unless the PIO device is in use. So, sharing a low use CD rom drive with a disk wouldn't be so bad. I am puzzled about the fallback to PIO concept. If a disk has gives some sort of timeout error or whatever, why would trying PIO correct the problem ? That seems equivalent to asking the disk to do the same thing, just more slowly. In my case, some sort of timeout error occurs on ad0, so it falls back to PIO, and works. A later access to ad1 also yields a timeout error, and then it drops to PIO, and works too. I'm fairly confident both disks did not experience media errors at the same time, which suggests a problem with the onboard IDE controller, or a driver bug. Tests continue... ---------------------------------------- This mail sent through www.mywaterloo.ca To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message