From:	"Michael Stewart" <mike AT reggin DOT freeserve DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: FASTEST DOUBLE BUFFERING?
Date:	Wed, 13 Jan 1999 23:13:02 -0000
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Eselk wrote in message <19990113010351 DOT 01578 DOT 00009727 AT ng36 DOT aol DOT com>...
>>You should consider using page flipping instead of double-buffering. As a
>>matter of fact, it's almost the same as double buffering with one except:
>>you do your rendering right into videomemory, so no data moving is needed.
>>You just change visible area on the screen from one page to another and so

>>on - this is obviously faster than double buffering


I would just like to disagree with the above and agree with the below :-)
Alot of computers have slower video memory than main memory. Rendering
direct
to video ram will not be very efficient (I think the video bandwidth will
cause bottlenecks
as well).
Possible the best way IMHO would be to:

- Render to a buffer in main memory
- Blit main memory over to the hidden video memory (should be very fast esp.
when
  optimised :-)
- Flip the active page over to the hidden page during the vertical retrace

if there is no hidden video memory (not all graphics cards have enough
memory) then
you can blit direct to the visible page during the retrace.

>Depending on your target market.  Many people still have slower VIDEO RAM
then
>CPU RAM, and in most VGA modes BANKS will slow you down and make programing
>virtual pages even slower.
>
>I like to use FPUCOPY on pentium machines for moving the double buffer.
Pretty
>fast.

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