From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261369AbULXEm3 (ORCPT ); Thu, 23 Dec 2004 23:42:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261373AbULXEm3 (ORCPT ); Thu, 23 Dec 2004 23:42:29 -0500 Received: from rproxy.gmail.com ([64.233.170.193]:7315 "EHLO rproxy.gmail.com") by vger.kernel.org with ESMTP id S261369AbULXEm0 (ORCPT ); Thu, 23 Dec 2004 23:42:26 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:references; b=rnQsAGUxRvWT5oLeRXv6BdzKa4tHU/v1o7Mh0AELx2r7DdngZxwjcEgAXezbd9x1d9ZwwJDnMbmOb5px0fvb5kPikdOTfNj0nGSG0x3vSJsF0XqJTIqFSq+XEn0vVEmoe4JJBvzhb+sEyRkWWOtOecGVgEjVPtk2Lxai/4bslSM= Message-ID: <8783be660412232042dd372c@mail.gmail.com> Date: Thu, 23 Dec 2004 23:42:26 -0500 From: Ross Biro Reply-To: Ross Biro To: Alan Cox Subject: Re: DMA problems with 3+ Promise IDE controllers Cc: Jaco van der Schyff , Linux Kernel Mailing List In-Reply-To: <1103845162.15233.9.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit References: <41CB1BE3.465BD490@netgroup.co.za> <1103845162.15233.9.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 23 Dec 2004 23:39:24 +0000, Alan Cox wrote: > On Iau, 2004-12-23 at 19:26, Jaco van der Schyff wrote: > > Any idea how I could get all three cards to work in UDMA100 mode? > > You either need multiple independant PCI busses or to write an > arbitrator for the IDE DMA layer to ensure that no more than two of the > three are doing DMA transfers at a time and the other waits. > Could you explain why they can't coexist on the same PCI bus. The only problem I see with having all three cards DMA at the same time is increased latency. But he's getting CRC errors on the transfer between the card and the drive, and that doesn't seem like a latency issue. I know Promise does funky stuff with their DMA, but I'm curious why no more than two cards can co-exist on the same PCI bus. Ross