Re: GX1-CS5530 sound problem !!!
From: Tech Support for IDE-CF (tech_at_ide-cf.info-for.us)
Date: 06/17/04
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Date: 16 Jun 2004 16:08:29 -0700
Jürgen Querengässer <msg1000@web.de> wrote in message news:<2jaqmaFv5g60U1@uni-berlin.de>...
> Tech Support for IDE-CF wrote:
>
> > Jürgen Querengässer <msg1000@web.de> wrote in message
> > news:<2j7iksFu5k7nU1@uni-berlin.de>...
> >> Tech Support for IDE-CF wrote:
> >> > We found that if you are running heavy sound I/O, i.e. mp3 and video
> >> > at the same time, the geode interrupt stack gets confused.
> >> >
> >> > The conflict is inside the geode companion chip, there is nothing you
> >> > can do about it.
> >> >
> >> > Our solution is to put it in graphic mode (even for simple text
> >> > display) for mp3. X appears to have less latency than the Geode's
> >> > Virtual VGA system. However, it does take up much more system memory.
> >> > On the plus side, system memory seems to be faster than the bios
> >> > memory anyway.
> >>
> >>
> >> Hi 'Tech Support for IDE-CF',
> >>
> >> I'm interested in how did you find this.
> >>
> >> I would like to know how I can provoke such behaviour. My app. also needs
> >> much CPU time and has to serve much interrupts and does video output.
> >> (Video uses the VESA-framebuffer device and afaik it doesn't need an
> >> interrupt. Furthermore the video memory is shared with the system memory
> >> (also in the virtual VGA mode [I think]) and should not slower or faster
> >> than X (unless X uses hardware acceleration; but this is possible in
> >> VEAS-mode, too.)
> >
> > I am using a 233 MHz (only 80 bogomips) Geode GX1. The performance is
> > disappointing, but barely enough for dedicated functions. Playing mp3
> > requires roughly 80% of CPU time on the chip. Our text mode mp3
> > player updates the play time every second, so there is a video reflesh
> > every second.
> >
> > In console text mode, the sound is distorted whenever the video
> > refresh occurs. Total system lock-up occurs once in a while.
> >
> > In X, the sound is smooth and mp3 plays for hours.
> >
> > Except for changing songs (audio is mutted), only one or two
> > characters on the screen are updated. My guess is that X only
> > updates the small region but the Geode VGA buffers compress and update
> > the whole screen all the time.
>
> I'm interested in the confused interrupt stack. How did you find out this?
That might not be the right words to use. But when it happens, the
video would stop refreshing for several minitues, than come back with
all the queued events (in X). It appears to be an internal watchdog
timer waking up the video chip. Anyway, we don't try to dig too deep
into the problem. As long as we multiplex the video and audio
properly, we can avoid the problem.
>
> Jürgen
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