Message-ID: <rZqZCdBGssG1EwZu@talula.demon.co.uk>
Date: Thu, 26 Mar 1998 21:39:18 +0000
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Cc: djgpp AT delorie DOT com
From: Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk>
Subject: Re: HELP::Plz check my code for some errors/optimization. (VESA.CPP)
In-Reply-To: <Pine.SUN.3.91.980326105139.29215G-100000@is>
MIME-Version: 1.0
Precedence: bulk

Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> writes:
>> In terms of working correctly, the BIOS text output function isn't
>> supported on every SVGA board
>
>Really?  On which ones?  And how does it fail?

Either it doesn't do anything, or it tries to write text as if this was
a standard VGA mode (which might produce garbage or draw onto the wrong
part of the screen).

I don't know exactly how many cards this will fail on, but from my
personal experience, text output didn't work at all in SVGA modes on my
old Tseng board, and on this Matrox it only functions correctly in 256
color modes (nothing is displayed in truecolor).

>I thought that BIOS function is the most reliable, if slow, method of
>writing text in any mode (you *are* talking about Int 10h/AH=0Eh,
>right?)  The Interrupt List doesn't have any caveats there, either.

From the VESA 2.0 specification, describing the ModeAttributes field:

     Bit D2 indicates whether the video BIOS has support for output
     functions like TTY output, scroll, etc. in this mode.  TTY support 
     is recommended but not required for all extended text and graphic 
     modes. If bit D2 is set to 1, then the INT 10h BIOS must support 
     all of the standard output functions listed below.


--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
"Pigs use it for a tambourine" - Frank Zappa