Mail Archives: djgpp/1998/09/17/02:45:10
ElvenForst wrote:
> Can anybody give me a description of VESA? How does it different from other
> video modes, such as 13h or ModeX?
>
> The reason that I'm asking is because my program is fine in ModeX or 13h, but
> when I switch to a VESA 2.0 driver, the image flickers and shutters. The
> program uses a double-buffering system that, for every animation frame:
> alwaysclears the entire buffer, redraws everything, and then blits to the
> screen. (The problem also occurs when I'm page flipping) The elements that are
> drawn _early_ are solid and stable, but the parts of the screen that are
> drawn_later_ are flickery and unstable.
Hmmm. Clearing the frame before the video card can switch to the new one...?
> Also, what is the difference between banked mode and the linear framebuffer
> drivers? (Besides that linear is faster.)
>
Banked mode forces you to only access a 64K chunk of video memory at a time. Some
cards have slightly different capabilities (multiple address space 'windows', 32K
banks, can only read from this one, can only write to that one, and crap like
that), forcing you to adapt your routines to labourously detect which banking
scheme is in use, and adapt your routines to switch banks when drawing to different
areas of the screen (been there, done that, didn't enjoy). Linear mode just lets
you access any address of video memory at any time (entire video memory is fully
addressable at all times) (haven't done yet, probably won't because OpenGL is more
productive).
(Note that I am not cutting up the VESA banked memory standard. I am cutting up
video card manufacturers that all went their seperate ways, arrogantly thinking
that their complex (or inexpensive) design is the best, screw compatibility and
standards. Or maybe the government should force companies to only make good
hardware...yeah...that's it...hahaha)
> Thanks-A-Million,
> --Richard Ellwood
Doug Gale
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