Mail Archives: djgpp/1999/07/01/17:31:16
On Thu, 1 Jul 1999, Endlisnis wrote:
> Sahab Yazdani wrote:
>
> > I needs lot of help with this one. Even with Assembly functions for
> > Drawing stuff, my scrolling routine is slow in 640X480. it works fine
> > in 320X200 (although hardware scrolling in mode X is still faster). but
> > with SVGA modes it just bombs out! Can anybody help me with some SVGA
> > scrolling routines? Possibly a site or tutorial that references these
> > things??
>
> Well, if you have enough ram, you can do hardware scrolling in SVGA.
> Also, something I've observed, in SVGA modes, it is usually MUCH faster to
> redraw the entire screen from a memory buffer than to do real scrolling
> because reading from video ram is sometimes up to 10 times slower than
> writing.
Well.... If you do hardware scrolling, you don't have to worry about
rebuilding the image.... If your method is copy the new image, then that's
software scrolling.... Hardware scrolling is the fastest available method
to scroll the screen.... All you have to do is change the content of 2
registers of the video hardware...
Unfortunately, hardware scrolling is not performed in a standard way...
Unless you use a standard API, such as the VESA one...
I've got a book I bought several years ago giving technical details about
several SVGA cards, but if no new edition is out, then the information is
obsolete...
--
Erwann ABALEA
erwann AT abalea DOT com
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