Date: Thu, 04 Jun 1998 16:53:30 -0700 From: Mike Smith <mike@smith.net.au> To: Stefan Esser <se@FreeBSD.ORG> Cc: shimon@simon-shapiro.org, Bob Willcox <bob@luke.pmr.com>, Michael Hancock <michaelh@cet.co.jp>, "freebsd-current@freebsd.org" <freebsd-current@FreeBSD.ORG>, tcobb <tcobb@staff.circle.net>, Karl Pielorz <kpielorz@tdx.co.uk>, Mike Smith <mike@smith.net.au>, Greg Lehey <grog@lemis.com> Subject: Re: DPT driver fails and panics with Degraded Array Message-ID: <199806042353.QAA02937@dingo.cdrom.com> In-Reply-To: Your message of "Fri, 05 Jun 1998 00:01:01 %2B0200." <19980605000101.27550@mi.uni-koeln.de>
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> On 1998-06-04 12:12 -0400, Simon Shapiro <shimon@simon-shapiro.org> wrote: > > Many of these problems are actually (arguabbly?) induced by timing problems > > on the PCI bus. Certain PCI-PCI bridges (or even motherboard ``main'' > > chipsets will deliver interrupts, I/O bus transactions and memory > > transactions out of order when hammered very rapidly, under heavy load, or > > both. We proved it clearly with certain ``industrial'' computers, and > > certain motherboards, by making the symptoms go away (or drastically > > change) as you move the DPT, video cards, Ethernet cards, etc. from slot to > > slot. > > This is a design "feature" of PCI, actually, and well documented. > > The interrupt lines are directly connected to the chip-set (or > possibly the CPU in non-Intel PCI systems) and for that reason, > there may for example be as many outstanding memory writes in > write-buffers as their FIFO depths allow, when the end-of-transfer > interrupt is recognized by the CPU. In case the clarification is of use; the idea here is that interrupt handlers will have some overhead, and the interrupt handler can be starting before the device's other activities have finished. Synchronisation is then performed as Stefan describes at the last moment to maximise concurrency. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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