From:	"Chaos" <chengin AT alpha DOT net DOT pl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: fprintf() and using under graphic modes
Date:	Thu, 25 Nov 1999 19:35:52 +0100
Organization:	Chaos Engine
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Kalum Somaratna aka Grendel napisał(a) w wiadomości:
<199911251149 DOT GAA38584 AT glitch DOT crosswinds DOT net>...
On 24 Nov 99, at 13:29, Chaos wrote:

> Do I really have to implement VESA 1.2 Bank Changing?
> I' ve searched within my friends someone with video card old enough not
> having VESA 2.0.
> I've only found 1 guy besides using UniVbe. So, do I must stick with slow
> (int 0x10 yuck!) bank changing?
> Thnx for eventual answer.

IMHO I think you should forget about VESA 1.2 bank switching
support and code specifically for the Linear Frame Buffer (VESA
2.0 and above).

AFAIK bank switching was implemented because the only way for
real mode programs to access video memory was thorough the
A000 range(64k). So if the card has 1MB vidram by bank switching
the real mode prog could acess all the 1Mb vidram in 64K banks.

However VBE 2.0 was designed  so that Protected Mode Programs
(DJGPP/DOS4GW  etc progs) can address the full memory as a
single linear buffer (instead of banking).

Most SVGA DOS games (Quake 1.00, MechWarrior etc) are also
designed so that they need at least VESA 2.0 as they use the LFB
for speed since all those  Vesa 1.2 int 10h bankswitching will be
very slow. So if you code only for VBE 2.0 you will in good
company.

Slow specially with mode switching (real-protect).

Also coding for the LFB is much more simpler and easier and you
will introduce less bugs than all those ancient bank switching stuff.

So IMHO you can program for the VESA 2.0 and distribute a copy
of UNIVBE with it that will enable VBE 2.0 support on any
computer that doesn't have it (like my VBE 1.2 card).

Phew :-) Thank god. Now I can get rid of that two branches in my prog: for
cool LFB and sloow compatible BnkSwtch.
But hey, can I redistribute my soft with SciTech's Univbe without any
copyrights law consequences? Is it free for spreading?

Wishing you sucess!
Kalum.

Thnx!

Take care.
-=| Chaos |=-
e-mail:  chengin AT alpha DOT net DOT pl
              chengin AT polbox DOT com

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