From owner-freebsd-stable Tue Apr 10 17:49:43 2001 Delivered-To: freebsd-stable@freebsd.org Received: from ece.cmu.edu (ECE.CMU.EDU [128.2.236.200]) by hub.freebsd.org (Postfix) with ESMTP id 2534E37B422 for ; Tue, 10 Apr 2001 17:49:38 -0700 (PDT) (envelope-from allbery@ece.cmu.edu) Received: from rushlight.rem.cmu.edu (ANNEX-5.ECE.CMU.EDU [128.2.136.5]) (authenticated) by ece.cmu.edu (8.11.0/8.10.2) with ESMTP id f3B0mgr13301; Tue, 10 Apr 2001 20:48:42 -0400 (EDT) Date: Tue, 10 Apr 2001 20:48:41 -0400 From: "Brandon S. Allbery KF8NH" To: Juha Saarinen , "Brandon S. Allbery KF8NH" , Cyrille Lefevre Cc: freebsd-stable@FreeBSD.ORG Subject: RE: ATA_ENABLE_ATAPI_DMA gone? Message-ID: <250770000.986950121@rushlight.rem.cmu.edu> In-Reply-To: X-Mailer: Mulberry/2.0.6 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wednesday, April 11, 2001 12:40:09 +1200, juha@saarinen.org wrote: +---- | :: As I understand it, ATA disks generally support DMA, and ATAPI devices | :: (floppies, tapes, CDROM/CDRW, etc.) generally don't; | | My understanding is that DMA is more efficient than PIO, so you'll find | that newer CD ROM drives (ditto DVD drives) support it, because of the | higher transfer rates provided. | | Slower floppy and tape drives on the other hand can get by with PIO. | | Don't think it's a device-specific issue, but I could be wrong. +--->8 Certainly early CDROMs falsely claiming DMA support caused pain in the Linux community until they split off ATAPI DMA support into a separate config option. One can hope that modern hardware doesn't have that problem, but I have little faith in PC hardware :) -- brandon s. allbery [os/2][linux][solaris][japh] allbery@kf8nh.apk.net system administrator [WAY too many hats] allbery@ece.cmu.edu electrical and computer engineering KF8NH carnegie mellon university ["better check the oblivious first" -ke6sls] To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message