[SDL] Double buffering in windowed and fullscreen modes

David Olofson david.olofson at reologica.se
Fri Aug 31 04:22:00 PDT 2001


On Friday 31 August 2001 03:16, Tyler Montbriand wrote:
> Trick wrote:
> > On Friday 31. August 2001 02:37, you wrote:
> > > When I do doublebuffering in SDL_FULLSCREEN, SDL_Flip() takes no
> > > time whatsoever.  In windowed mode, however, it takes 12-20ms, as
> > > measured by SDL_GetTicks().  What causes this slowdown?
> >
> > Hardware flipping in fullscreen and software flipping in windowed
> > maybe ? What graphics card do you have ?
>
> I've got a Geforce256.  I can understand some slowdown, but 12ms?
> That's horrible!

Well, yes, 12 ms *is* horrible. Sounds like it's the CPU that has to do 
the transfer, as is normally the case on Linux. AFAIK, Windows *should* 
support DMA transfers, but either I'm wrong, or something in your setup 
is...

Well, unless, of course, you're running at 1280x1024, 32 bit. :-) Such a 
buffer takes a minimum of 10 ms to transfer over AGP 1x, if everything is 
theoretically perfect. (Which is never the case in real life...)


//David Olofson --- Programmer, Reologica Instruments AB

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