From: xmerm05 AT vse DOT cz (Mertl Michal - UC,,student,UID=22797)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Vesa 2.0 is slower than 1.2 on my video card !!!!!
Date: Fri, 25 Jul 1997 09:21:50 GMT
Organization: University of Economy, Prague
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(Ricardo Cunha) writes:
>>No SIR!
>>VESA is a software API. SDD >is< VESA 2.0, not an emulation.
>>The difference between SDD and your card is that SDD goes TSR, but your
>>card is in ROM from the start.
>>
>>Guess why it's in ROM, folks.. it's software :)
>>VESA is an API, which means that instead of having a gazillion different
>>calls to put a pixel on a screen, you only do one, and VESA picks the
>>right one for your video card.
>>
>>VESA translates, but not from 2.0 > 1.2 - it translates VESA calls to
>>direct hardware writes.

>That's right but...

>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

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