Message-Id: <199811062259.WAA22277@remus.clara.net>
From: "Arthur" <arfa AT clara DOT net>
To: <djgpp AT delorie DOT com>
Subject: RE: "Droppings" in Allegro 16 bit color mode on Trident Card
Date: Fri, 6 Nov 1998 22:59:20 -0000
X-Priority: 3 (Normal)
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook 8.5, Build 4.71.2173.0
Importance: Normal
In-Reply-To: <000701be09b7$4d9db980$9c6f19c4@default>
X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3
Reply-To: djgpp AT delorie DOT com

> I have a problem - I seem to get "droppings" on the screen when using
> Allegro's 16bit color modes on my 4meg Trident AGP SVGA card. This mainly
> happens when I blit stuff around - it is not very obvious (small areas of
> pixels get dropped or color changed). The same thing happens in some
> programs (notably Duke Nukem 3D) that use the 640x480x256 mode. However,
> Windoze (which also runs in 640x480x16bit on my system, just like the
> Allegro DJGPP program I am working on) works PERFECTLY - no droppings
> anywhere. These "droppings" also happen when clearing a bitmap (like the
> screen, for example) - not everything gets turned to black some pixels
> remain from the old image.
>
> Any ideas? Is something wrong with my card? Drivers? Since it works 100%
> when in Win, I surmise that the Allegro drivers must be
> incompatible with my
> card somehow - will it help to get UniVbe? What can I do to test
> if there is
> a true incompatibility?

The problem is not with Allegro, but with your card's manufacturer. They
have supplied dodgy drivers. Visit their web site and bother them until they
give you some new ones. Windows doesn't use DOS standards (such as VESA),
and some manufacturers have stupidly decided to ignore DOS and just support
Windows screen modes.

UniVBE probably will halp, but I'd try your manufacturer first, because it's
cheaper :-)

James Arthur
jaa AT arfa DOT clara DOT net
ICQ#15054819