From owner-freebsd-hackers Thu Jul 6 12:53:43 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from bingnet2.cc.binghamton.edu (bingnet2.cc.binghamton.edu [128.226.1.18]) by hub.freebsd.org (Postfix) with ESMTP id A475337C22C for ; Thu, 6 Jul 2000 12:53:38 -0700 (PDT) (envelope-from zzhang@cs.binghamton.edu) Received: from sol.cs.binghamton.edu (sol.cs.binghamton.edu [128.226.123.100]) by bingnet2.cc.binghamton.edu (8.9.3/8.9.3) with ESMTP id PAA01656 for ; Thu, 6 Jul 2000 15:53:37 -0400 (EDT) Date: Thu, 6 Jul 2000 15:51:34 -0400 (EDT) From: Zhihui Zhang To: freebsd-hackers@freebsd.org Subject: Max DMA size Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Can anyone tell me what factors determine the max DMA size (DMA counter on each controller or PCI bus related)? What is the typical max DMA size for a SCSI disk connected to a PCI bus? It seems to be much larger than MAXPHYS (128K). If so, does it mean we are not using full potential of DMA? So what's the problem if we enlarge MAXPHYS? Any help is appreciated. -Zhihui To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message