Message-Id: <m0viKId-000S1sC@natacha.inti.edu.ar>
Comments: Authenticated sender is <salvador AT natacha DOT inti DOT edu DOT ar>
From: "Salvador Eduardo Tropea (SET)" <salvador AT natacha DOT inti DOT edu DOT ar>
Organization: INTI
To: Ove Kaaven <ovek AT arcticnet DOT no>, djgpp AT delorie DOT com
Date: Thu, 9 Jan 1997 16:23:15 +0000
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Subject: Re: Newbie needs Help! Allegro + W95   :-(


> Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk> wrote:
> 
> >The problem is, I think, with the vsync() call. Win95 seems very erratic
> >in it's handling of retrace syncing. Sometimes it works, sometimes it
> >doesn't, which is very irritating (if only IBM had seen fit to include a
> >retrace interrupt in the VGA design!).
> 
> This may not have been in the *original* IBM VGA card, but according
> to my old book in programming for PC video subsystems, the EGA, the
> VGA, and the MCGA supports generating a Vertical Interrupt on IRQ2
> whenever vertical retrace starts, and explains how this is done. On
> the EGA/VGA, these interrupts appears to be controlled by the CRTC
> Vertical Retrace End register (CRTC register 11h) bits 4 and 5, though
> I haven't really studied this in detail.

  Is true the controler even have some features for that, but if I 
remmember well only some PS/2 VGAs have it really implemented. 

SET
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Salvador Eduardo Tropea (SET).
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