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Date: Fri, 30 Jul 2004 14:17:13 +0200
From: Maxime Henrion <mux@freebsd.org>
To: Maxim Sobolev <sobomax@portaone.com>
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Subject: Re: Is there still sufficient reason for hw.ata.atapi_dma being 0
	by default?
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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.
> 
> I easily imagine newbies who make a conclusion that "FreeBSD sucks" 
> after installing FreeBSD and finding that they can't burn CDs, while 
> other operating system do it without any problems.

I think it should be enabled by default when the DMA mode of the ATAPI
device is UDMA33 or higher, not when it's WDMA2.  The atapi_dma sysctl
is off by default to guard against buggy ATAPI devices which are
incorrectly reporting themselves as being able to do DMA, however
I think this mostly applies to old devices, which won't do UDMA33 or
higher.  Soren would know better than me though.

Cheers,
Maxime