From: Myke AT cyberdude DOT com (Ricardo Cunha)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Vesa 2.0 is slower than 1.2 on my video card !!!!!
Date: Fri, 25 Jul 1997 18:21:10 GMT
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>>When a board suports Vesa 2 Vesa calls to direct hardware writes but a
>>board only supports Vesa 1.2 and we use a emulator then the emulator
>>translates Vesa 2 Calls to Vesa 1.2 and send the information to the
>>board that calls direct hardware calls. As you see the emulator spends
>>time converting from Vesa 2 to Vesa 1.2
>
>Are you sure you know what you are talking about? Vesa 2 is an extension, it 
>does lot more than 1.2. Vesa 2.0 functions can't be decompiled to VESA 1.2 
>calls. SDD must know everything about the card to be able to provide VBE20 
>on it, so it can do hardware level (register) writes.
>
>Also usually programs from ROM runs slower than from RAM, that's why the 
>shadowing is often used, so the TSR would with the same program be probably 
>faster.
>
>Michal

When a board suports Vesa 1.2 it's prepared to be fast with that calls
but when a board doesn't suport Vesa 2.0 that kind of calls don't do
anything. It's necessary to translate to Vesa 1.2 or to native calls.
The major modification it's the linear mode. In this case, it's used a
buffer as the video memory to retain the game (Vesa 2) calls and then
the buffer it's send to the board with Vesa 1.2 or native calls.
In some boards it's used native calls, in others is used Vesa 1.2
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Ricardo Cunha
myke AT cyberdude DOT com
http://www.geocities.com/Area51/Cavern/7471
ICQ: 2217830
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