If it is transient, that is, it's just noise that appears during
graphics operations and is not corruption that is permanent in
the framebuffer, then this is a memory contention issue. There
is not enough video ram bandwidth for the DAC to scan out the
framebuffer and have the graphics accelerator access the framebuffer
at the same time. Typical causes:
1) Memory clocks are programmed too low.
2) Memory clocks may be correct, but other memory timing parameters
are incorrect, potentially including parameters governing
graphics accelerator access priority to the video ram.
3) All memory timings are correct and the card just can't scan out
the framebuffer this quickly. Meaning this color depth, resolution,
or refresh rate is beyond the cards capabilities. Specifically,
the modeline's pixel clock times the number of bytes per pixel
is the DAC's memory bandwidth requirement and it is too high.
Mark.
On Mon, 21 Jul 2003, Vladimir wrote:
> Hey i am completely stumped by this, maybe someone can help me out.
>
> I am using the trident frame buffer device and I have attached my X
> config file, the problem i seem to be having is this. Whenever there is
> any sort of changes happening on screen (by changes i mean if the image
> on screen changes in any way i.e. typing in text, animatins, moving
> windows) there appears a distortion across the screen. It is hard to
> describe but it looks like groups of single pixle-wide lines that look
> like they have been shifted horizontaly. The only time this does not
> happen is if nothing is changing on screen the the ammount of distortion
> is proportional to teh ammount of things changin on screen. Can anyone
> help me with this?
>
>
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