[vox-tech] update on the audio CD problem

[Peter Jay Salzman]

On Fri 27 Jan 06,  1:17 PM, Micah J. Cowan <micah at cowan.name> said:
> On Fri, Jan 27, 2006 at 04:05:23PM -0500, Peter Jay Salzman wrote:
> > On Fri 27 Jan 06, 12:50 PM, Bill Kendrick <nbs at sonic.net> said:
> > > On Fri, Jan 27, 2006 at 05:06:09AM -0500, Peter Jay Salzman wrote:
> > > > Digital extraction is where the cd is read, and the signal gets pumped
> > > > through the ATA port to your speakers.  This is more efficient from the
> > > > CPU's standpoint.
> > > 
> > > Woah, I would think this is way LESS efficient.
> > 
> > No.  The CPU is involved in many read-copy operations when the signal passes
> > through the sound card.
> > 
> > AFAIK, the north and south bridge use DMA during digital extraction.
> 
> Pete, I'm pretty sure that the CPU isn't even /involved/ with analog
> mode. It's analog. There is no read/copy. There's nothing to read/copy.
 
sure there is.

data needs to be copied from kernel space to user space.  that _definitely_
requires the CPU.  that's why the whole "zero-copy user-space access" was
such a big deal.

pete