<h2>Video Killed the Audio Card</h2>

Several years ago the manufacturers of PCI video cards discovered a way to increase their performance by playing unfairly with the PCI bus. This can put a lot of awful "zipper" noise into the audio output when you move windows around the screen.

A Possible Solution

Check your XF86Config file and see if there is a line like   
    this: 'Option "pci_retry"'

It would be under the "Device" section. Try commenting it 
    out and see if that helps. Or try adding this line, if it's 
    not there. I'm not sure
    which is the "right way". It didn't make a difference for 
    me, but then I don't have a PCI soundcard.

Another Possible Solution

Try an AGP video card instead of PCI. Pix writes,

"After looking around, it seemed that AGP was the way to go  
    to stop getting audio dropouts whenever some video event
    occurred. This guess was based on the common explanation 
    that the pops are caused when the PCI video card steals the
    whole bus to do some operations. Since AGP is a different 
    bus altogether, it seemed like a good step.

"And I can say, at least at first glance, that it seems to 
    be the way to go. At home, I had a Trio64, which recieved 
    many pops and clicks (even when doing somet hing reasonably 
    low on CPU usage). At work, I have a PIC Riva128 card, which
    also gets pops and clicks during focus changes etc. Just 
    recently I purchased an AGP RivaTNT2 card, and I haven't   
    been
    able to generate an audible dropout yet. PureData still 
    occasionally reports DIO errors, but I haven't heard any of 
    them yet.

"Since it's quite hard to get a non-AGP card nowadays, this 
    has to be good news for linux audio :) "

What Causes the Video Card Problem

As mentioned above, a PCI video card tries to hog the PCI 
    bus to increase its own performance. This interferes with 
    other devices on
    the bus, including soundcards.

There is a good description of the problem at 
    http://www.zefiro.com/vgakills.txt

Note that their list of solutions are all for Windows device 
    driver settings. The only thing there that seems to have a 
    clear analogy for
    Linux is the "pci_retry" option in your XF86Config file.

Note:I have also seen some anecdotes on 
    comp.sys.ibm.pc.soundcard.tech that some VIA chipset-based 
    motherboards, especially
    those with the VIA MVP3, are especially prone to this 
    problem, and may also have problems with using UDMA mode for 
    hard drives. I
    don't have much real information about this except that some 
    people seem to like Asus motherboards better. Note that all 
    these reports
    were from people running Windows 95 or 98... maybe that's 
    their problem.

* A Partial List of BadVideoCards that may cause these problems.