Mail Archives: djgpp/1998/07/20/01:31:34
a DOT gillett AT virgin DOT net (Andrew R. Gillett) writes:
>In comp.os.msdos.djgpp, article <mvparvia DOT 900873261 AT snakemail DOT hut DOT fi>,
>Mikko V.I. Parviainen (mvparvia AT kvartsi DOT hut DOT fi) wrote:
>> a DOT gillett AT virgin DOT net (Andrew R. Gillett) writes:
>> >I've never understood the point of double-buffering. Are there any
>> >advantages over page flipping?
>> Some time ago I made some tests in 640*480*256 mode. I have an P100
>> machine, with some very bad SVGA card.
>> My test program used the whole screen. First, I tried page flipping.
>> It was annoyingly slow, so I decided to try double buffering,
>> because it was very quick to code. The speed gain was unbelievable.
>> The blit was about two times as quick as with double buffering.
>> I think that the cause of this effect was the slowness of
>> video memory, but I am not sure.
>I can't see how double-buffering could be faster than page flipping. Were
>you using vsync() in the double-buffering version? If not, that's why it
>ran faster.
Actually, the only function I changed betweeen these versions was
page_flip(), which in the page flipping version flipped video memory
pages and in the double buffering version copied the buffer to screen.
It has been awhile, but iirc there was a vsync in both versions.
I was very cnfused by the result myself. Perhaps I should check the
sources again.
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Mikko Parviainen
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