Re: Direct access to paged Video ram

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From: Matan Ziv-Av (matan@svgalib.org)
Date: Wed 08 Nov 2000 - 00:06:18 IST


On Mon, 6 Nov 2000, Richard A. Smith wrote:

> >vga_drawpixel is certainly too slow. vga_drawscanline is almost as fast as
> >can be.
> 
> Yeah but you can still see it draw... I need to totally draw in video memory and then flip
> to that section.

Can you show the code you use? I don't see any way for a loop of
drawscansegments from system memory to video memory being noticeably
slow on any pentium class machine. Can you run bankspeed, at 1024x768
with 16 bits (export SVGALIB_DEFAULT_MODE=G1024x768x64Kand tell me the
results?

On my TNT2, native driver gets 1.46s, and vesa driver gets 20.95s. (that
is for approximately 600,000 bank switches. 

Copying a whole (640x480x256) screen with vga_drawscansegment takes
either 5 or 485 bank switches.

For page flipping, draw the second page at lines 480-959 (using
drawscansegment), and use vga_setdisplaystart(640*480) to display the
second page.



-- 
Matan Ziv-Av.                         matan@svgalib.org



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