From: Gregory Huczynski (greg@dcs.gla.ac.uk)
Date: Tue 07 Aug 2001 - 12:38:08 IDT
Hi, Trying to get the maximum speed out of svgalib, I implemented double buffering in video memory. Unfortunately, this version is actually slower than my original one! First version: write to a memory frame buffer in main memory and, on a screen update, copy the buffer to video memory using a fast assembler memcpy. Speed is ~30fps. Second version: have two frame buffers in video memory. Write to one of the frame buffers and, on a frame update, set the display pointer to the written buffer using vga_setdisplaystart. On the next frame, make updates to the other buffer, and then change the pointer again. Speed is ~21fps. On a theoretical level, I thought that the second version would be faster, as I'm writing directly to video memory and only change one pointer to update a frame; in contrast, in the first version, I have to do a memory copy to update a frame. Any ideas why double buffering in video memory is actually slower? Thanks in advance Gregory Huczynski ------------------------------------------------------------------ Unsubscribe: To: listbot@svgalib.org Body: unsubscribe linux-svgalib
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