Date: Fri, 15 Feb 2002 11:10:55 -0800 From: "Kevin Oberman" <oberman@es.net> To: Cliff Sarginson <cliff@raggedclown.net> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: DMA on ATAPI CD's [ Was Re: About printers ] Message-ID: <20020215191055.50E1E5D09@ptavv.es.net> In-Reply-To: Your message of "Fri, 15 Feb 2002 19:58:50 %2B0100." <20020215185850.GC1394@raggedclown.net>
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> Date: Fri, 15 Feb 2002 19:58:50 +0100 > From: Cliff Sarginson <cliff@raggedclown.net> > Sender: owner-freebsd-questions@FreeBSD.ORG > > On Fri, Feb 15, 2002 at 10:25:16AM -0800, Kevin Oberman wrote: > > > Date: Thu, 14 Feb 2002 22:46:58 +0100 > > > From: Cliff Sarginson <cliff@raggedclown.net> > > > Sender: owner-freebsd-questions@FreeBSD.ORG > > > > > > On Sat, Jan 09, 1999 at 05:09:35PM +0300, vanya wrote: > > > > > > <snip> (Best to keep unrelated questions in seperate posts). > > > > > > > And one question about DMA for EIDE disks and ATAPI CD. Is DMA automatically > > > > enabled or user must turn on this option? > > > > > > I believe DMA is not enabled on ATAPI CD devices, I believe it is > > > considered a source of possible instability in certain cases (I know > > > of no proof for this..) .. you can forceably re-enable it by an entry > > > in sysctl.conf. I have 2 IDE i/faces, with a hard drive and a CD/DVD > > > on one slave and a CD R/W on another. My line looks as follows: > > > > > > hw.atamodes=dma,dma,dma,dma > > > > > > You will need to adjust this according to your actual IDE setup, > > > (i.e. how your ide's are actually configured)... > > > > > > "man 8 sysctl.conf" may help. > > > > On almost all systems you really want to add hw.ata.atapi_dma="1" to > > /boot/loader.conf to enable DMA on ATAPI devices. > > > > The reason it is disabled by default is that some early ATAPI > > controllers did not work correctly (at all) in DMA mode. Since it is > > considered critical that CDs be accessible from the GENERIC kernel to > > do the initial installation, all ATAPI access had to default to PIO. > > > > The only way to be sure about this is to turn on DMA and see of the CD > > works. (It almost certainly will.) > > > > This is a parameter that must be set before the ATA driver is started, > > so it cannot be put in sysctl.conf. It must be in /boot/loader.conf. > > > I think this is incorrect, it can be put in sysctl.conf, and I believe > it works if you do it as I stated. When I try this I get: sysctl: oid 'hw.ata.atapi_dma' is read only R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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