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From: rommel@Informatik.TU-Muenchen.DE (Kai-Uwe Rommel)
Newsgroups: comp.windows.ms
Subject: slowness of screen drivers
Message-ID: <1991Jun7.100103.8975@Informatik.TU-Muenchen.DE>
Date: 7 Jun 91 10:01:03 GMT
Sender: news@Informatik.TU-Muenchen.DE
Organization: Technische Universitaet Muenchen, Germany
Lines: 46

During the last time I tested several VGA cards using Tseng 4000 and
Trident 8900 chip sets. I have tested all modes (if drivers were
available) and did benchmark tests.

I have tested the cards under Windows 3.0 and under OS/2 1.3
Presentation Manager. Especially I was interested in the 1024x768x16
drivers because 256 color drivers are much too slow to be usable and are
not required for most purposes.

For both chip sets I got the newest drivers from cica.cica.indiana.edu
for Windows and the OS/2 drivers from a site in Finland.

The OS/2 drivers were 800x600x16 and 1024x768x16 only for both chip
sets. 

Now the results. All drivers&cards worked well under both environments.
But the speed was different. What I was especially interested in was
simple screen to screen bitblt's because users very often move Windows
around on the screen and the speed of these moves is important.

I was surprised by the speed of the OS/2 drivers. On my (not so fast)
24MHz 386 windows almost instantly moved to their new positions,
nothing of the moving process was visible on the screen. This applies to
both chip sets although the Tseng 4000 was a bit faster.

Now, under Windows 3.0 the moving of windows on the screen is
unbelievable slow in comparison to OS/2. This too applies to both chip
sets although here too the Tseng 4000 is faster (significantly). Moving
a window of about 700x450 on the 1024x768 display took about or more
than a second (!!!) on both cards. One can view every scan line beeing
copied. This was not a problem of my particular machine configuration or
Windows 3.0 installation but occured on several tested machines.

Has anyone an explanation for these big differences in window moving
speed of these two environments? This is even more surprising as both
are basically 16 bit environments and are based on similar technology.

I am not talking about 20% or even 50% of speed difference but almost
an order of magnitude!

Kai Uwe Rommel

/* Kai Uwe Rommel, Munich ----- rommel@lan.informatik.tu-muenchen.dbp.de */

DOS ... is still a real mode only non-reentrant interrupt
handler, and always will be.                -Russell Williams