Re: is there a buffer?

Lucas Vogel (lucas7@home.com)
Sat, 09 Sep 2000 19:45:52 -0700


I tried switching the BIOS setting and it didn't change anything; in fact it
almost seemed to make things worse. 

It also doesn't seem to make any sense. If I switch to KDE I don't have these
problems, and KDE to me almost seems like a much bigger, bulkier desktop
manager. I have an 8 MB video card, plus a Voodoo Card (I don't know if it's
even being used or not), so video memory should not be an issue for me;
nevertheless I seem to have problems. 


John Gruenenfelder wrote:
> 
> The reasoning I've heard is bus saturation.  You move a large window so the
> video card must transfer a lot of data.  For 1024x768x32 that's about 3.1MB
> for a full screen update, which happens many times as you drag the window.
> 
> Most modern video cards have an option for bus mastering.  This is usually on
> by default.  What this means is that when the video card is transferring all
> of that data, it takes complete control of the bus until the transfer is
> done.  This is hand because it results it better performance for your video
> card.  Because of this, giving your music player a larger buffer won't help
> because that data still has to travel over the bus where the bottleneck is.
> 
> To fix this you can:
> 1) work in a lower color depth resulting in less data.
> 2) turn off bus mastering.  Usually in your BIOS there is an option to "Assign
>    IRQ to VGA".  Turning that off should disable bus mastering.  If not, there
>    should be an X server option.  Of course, this will reduce the performance
>    of your video card.
> 
> --John Gruenenfelder    Research Assistant, Steward Observatory, U of Arizona
> elrond@azstarnet.com    johng@bach.as.arizona.edu
> "This is the most fun I've had without being drenched in the blood
> of my enemies!"
>         --Sam of Sam & Max
> 
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