Apple ATA DMA problems with ATAPI

[Justin Hibbits]

On Mon, Mar 23, 2009 at 10:07:57AM -0700, Marcel Moolenaar wrote:
> 
> On Mar 22, 2009, at 2:54 PM, Justin Hibbits wrote:
> 
> > On Sun, Mar 22, 2009 at 01:41:18PM -0700, Marcel Moolenaar wrote:
> >>
> >> On Mar 22, 2009, at 11:06 AM, Justin Hibbits wrote:
> >>
> >>> Well, it seems I was bitten by the ATA DMA problems from a few
> >>> months back.
> >>
> >> Try disabling DMA for atapi in /boot/loader.conf and enable
> >> it in /etc/sysctl.conf. For some reason, on my Mac Mini at
> >> least, it helps to first program PIO and then program *DMA.
> >>
> > It appears hw.ata.atapi_dma is a read-only tunable, so /etc/ 
> > sysctl.conf has no
> > effect on it, and only throws a warning about being unable to change  
> > it.  It's
> > working sufficiently as PIO, though.
> 
> 
> Hmmm... I misremembered. Use atacontrol to set the mode:
> 
> mini-g4% sudo atacontrol mode acd0 wdma2
> current mode = WDMA2
> 
> FYI,

Yeah, I tried that last night right after I sent the email.  It failed just as
spectacularly, slowing down the machine to an unusable crawl as well.  Going to
try Nathan's patch as soon as I get home to reboot.

- Justin