Date: Sat, 13 May 2006 22:20:07 +0300 (EEST) From: Dmitry Pryanishnikov <dmitry@atlantis.dp.ua> To: Marcin Jessa <lists@yazzy.org> Cc: des@des.no, harikurniawan@gmail.com, current@freebsd.org Subject: Re: DMA no active on HL-DT-STCD-RW/DVD Message-ID: <20060513221144.O16055@atlantis.atlantis.dp.ua> In-Reply-To: <20060513183648.7444b11b.lists@yazzy.org> References: <4c40c4e70605130152s52fb3188nd847a0b8b0d46972@mail.gmail.com> <861wuy8b84.fsf@xps.des.no> <4c40c4e70605130418y3208840ctb0b1c7b1f61b7a74@mail.gmail.com> <86wtcq6psi.fsf@xps.des.no> <4c40c4e70605130659q4c486a64u188177bd5eb804f5@mail.gmail.com> <86hd3u6lbc.fsf@xps.des.no> <4c40c4e70605130744o5d0fd566n6a219ade5924561d@mail.gmail.com> <86d5ei6k3x.fsf@xps.des.no> <4c40c4e70605130835v46296d6akcc0bdd44bec49d08@mail.gmail.com> <20060513190519.P16055@atlantis.atlantis.dp.ua> <20060513183648.7444b11b.lists@yazzy.org>
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Hello! On Sat, 13 May 2006, Marcin Jessa wrote: >> WDMA corresponds to so-called "multiword DMA" transfer mode. It's slower than >> UDMA (IIRC WDMA2 gives 16Mbytes/s, same as PIO4), but still should be >> sufficient for CD/DVD drive (well, up to 8x-speed DVDs). Of course, it's >> better to use WDMA2 than PIO4 because WDMA (as well as UDMA) doesn't use >> CPU cycles for moving data between RAM and device. FreeBSD's ata driver >> is quite conservative, and doesn't automatically enable WDMA mode for >> ATAPI device even if hw.ata.atapi_dma=1, so you should just enable >> this mode with atacontrol. E.g., you can add > > Does this mean I should set my laptop's drive mode to WDMA2 instead of > UDMA100 (HD) and UDMA33 (CDRW)? No, there is no point in using WDMA if your hardware works well in UDMA mode. UDMA is faster (at least twice) than WDMA2, and provides data CRC check = more reliable. But if device supports _only_ PIO and WDMA, it's better to use WDMA mode. > Marcin. Sincerely, Dmitry -- Atlantis ISP, System Administrator e-mail: dmitry@atlantis.dp.ua nic-hdl: LYNX-RIPE
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