Why is ATAPI DMA disabled by default ?

[Brooks Davis]

On Thu, Aug 14, 2003 at 01:45:45AM +0300, Alexander Serkov wrote:
> I use 5.1-current and have found that by default FreeBSD disables ATAPI's 
> support for DMA transfers and thus uses CPU hungry PIO modes.
> It even makes sysctl used to change this read-only.
> I had changed the default value of atapi_dma to 1 in dev/ata/atapi-all.c to 1 
> and it worked fine for me.
> Can someone explain why it is disabled?

Lots of drives, even fairly new ones be well know vendors, hang the
system during boot if ATAPI DMA is enabled because they lie about
supporting it.

-- Brooks

-- 
Any statement of the form "X is the one, true Y" is FALSE.
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