ubb-vga, with DMA

Werner Almesberger werner at almesberger.net
Sun May 1 16:04:10 EDT 2011

After a bit of a struggle, I finally got DMA to work well enough
that I get a stable image at 1024x768:


Note the absence of the horizontal stretching near the right edge I had
before DMA:


Here's a screenshot of a real-life application, taken on my PC and
displayed by my Ben:


The steep angle is an attempt to avoid the substantial darkening I
get at the top of the screen. Somehow my camera and the monitor seem
to be conspiring in the production of this effect ...

Full disclosure: only 1024x768 looks good at the moment. 800x600 has
a lot of artefacts and 640x480 even locks up the DMA controller,
requiring a reboot to fix it.

- Werner

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