Søren Schmidt wrote: > Chuck Swiger wrote: > >> Søren Schmidt wrote: >> >>> Maxim Sobolev wrote: >>> >>>> Since high-speed CD-RW/DVD-RW recorders (32x - 52x) are commodity >>>> now IMO it makes sense to review hw.ata.atapi_dma default of 0, >>>> since apparently PIO mode can't support necessary sustained data >>>> transfer rates anymore. For example I had had problems burning RWs >>>> on 16-24x with several drives in PIO mode, which gone when I've >>>> switched to DMA. >> >> >> >> Before CD burners became common, having this sysctl default to zero >> was almost entirely harmless: people would simply read from CD-ROM >> drives slower than optimal. If we change the default to one, people >> with fast burners will no longer generate coasters by default too. In >> other words, Maxim has provided a pretty good reason for changing the >> default of atapi_dma, I think. :-) > > > Actually not, most if not all modern fast burners implements some sort > of "burn proof" ie no coasters at all due to buffer underruns... Actually it was not looking like underruns. I had weird problems burning RWs at 24x in PIO with three different burners - the burncd process just hanged solidly at random position, only atacontrol reinit helped. Machine was 100% idle (Celeron 2.4GHz). Switching to DMA33 solved the problem. -Maxim > >>> Hmm, things are still messy, but most drives that support UDMA33 can >>> do ATAPI dma. However, that is only part of the equation, the chipset >>> has its hands in there as well, and unfortunatly there seems to be no >>> good way to detect when it works and when it doesnt. >> >> >> >> If the chipset is broken, why doesn't it default to using PIO4 rather >> than UDMA? :-) Anyway, doesn't there exist fallback code in >> dev/ata/ata-disk.c: >> >> /* if this is a UDMA CRC error, reinject request */ >> [ ... ] >> printf(" falling back to PIO mode\n"); >> >> ...which will switch a device generating errors from UDMA mode to >> PIO? Can this check also turn off using atapi_dma (if using PIO >> doesn't already imply not using DMA)? > > > Not really, the problem with ATAPI dma is that if it fails it most > likely locks up the machine, so there is no way to back pedal... > > -Søren > > >Received on Sat Jul 31 2004 - 12:52:44 UTC
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