From:	Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: VBE 2.0 Pmode Bank Switching...
Date:	Fri, 14 Feb 1997 20:09:17 +0000
Organization:	None
Distribution:	world
Message-ID:	<HCniXKAtZMBzEwdx@talula.demon.co.uk>
References:	<Pine DOT SUN DOT 3 DOT 95 DOT 970210105100 DOT 26202A-100000 AT linknet DOT kitsap DOT lib DOT wa DOT us>
	<5duo1r$5vr$1 AT mack DOT rt66 DOT com> <33049326 DOT 5B09 AT eev DOT e-technik DOT uni-erlangen DOT de>
NNTP-Posting-Host:	talula.demon.co.uk
MIME-Version:	1.0
Lines:	19
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Schuster writes:
>What's the difference between the vesa modes? Is it the speed?
>just to be answered in short terms, no asembler code

Yup. With VESA 1.x, every time you switch banks (this has to be done
several times during most drawing functions), you have to call a 16 bit
real mode interrupt function, which involves the cpu switching from
protected mode into real mode and back. This is slow...

With VBE 2.0, you get protected mode functions for doing the bank
switching, which avoids the mode switch and is therefore a lot faster.
And on most recent cards, VBE 2.0 lets you use a linear framebuffer,
which removes the need for bank switching altogether, making graphics
coders very happy :-)

/*
 *  Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
 *  Ghoti: 'gh' as in 'enough', 'o' as in 'women', and 'ti' as in 'nation'.
 */

- Raw text -