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
MIME-Version:	1.0
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
--------------- 0 --------------------------------
Salvador Eduardo Tropea (SET).
Address: Curapaligue 2124, Caseros, 3 de Febrero
Buenos Aires, (1678), ARGENTINA
TE: +(541) 759 0013

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