From owner-freebsd-questions Sun Jan 5 20: 4:53 2003 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A014D37B405 for ; Sun, 5 Jan 2003 20:04:50 -0800 (PST) Received: from empire.explosive.mail.net (empire.explosive.mail.net [205.205.25.120]) by mx1.FreeBSD.org (Postfix) with SMTP id 6053D43EA9 for ; Sun, 5 Jan 2003 20:04:49 -0800 (PST) (envelope-from mykroft@explosive.mail.net) Received: (qmail 5715 invoked from network); 6 Jan 2003 04:03:53 -0000 Received: from ticking.explosive.mail.net (HELO ticking) (205.205.25.116) by empire.explosive.mail.net with SMTP; 6 Jan 2003 04:03:53 -0000 Message-ID: <001e01c2b538$c1375460$7419cdcd@ticking> From: "Adam Maas" To: "Bruce Campbell" , Cc: References: <1041368236.3e1204ac45da5@www.nexusmail.uwaterloo.ca> <025701c2b112$ddfbf580$1200a8c0@gsicomp.on.ca> <1041371397.3e121105cdf30@www.nexusmail.uwaterloo.ca> <1041822086.3e18f1868e32c@www.nexusmail.uwaterloo.ca> Subject: Re: ata "fallback to PIO mode" on dual processor AMD systems Date: Sun, 5 Jan 2003 23:04:48 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG This would be legacy behaviour from the days of buggy ATA33/UDMA implementations, where falling back to PIO mode would allow a device with a buggy UDMA implementation (Unfortunately rather common at the time) to function. --Adam ----- Original Message ----- From: "Bruce Campbell" To: Cc: Sent: Sunday, January 05, 2003 10:01 PM Subject: Re: ata "fallback to PIO mode" on dual processor AMD systems > 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-questions" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message