From: mlevis@ringer.cs.utsa.edu (Mike Levis)
Subject: Re: Slow scrolling in DOS solved
Organization: University of Texas at San Antonio
Date: Sat, 7 Nov 1992 09:50:01 GMT

In article <1992Nov7.012255.22631@monu6.cc.monash.edu.au> parry@yoyo.cc.monash.edu.au (Tom J Parry) writes:
>I decided to play with my DOS settings this morning and I have sped up my
>DOS scrolling by a factor of 10.
>
>I have a Tseng Labs ET4000 Mega/Eva 2 and decided to turn off the
>VIDEO_ROM_EMULATION. Seems the ET4000 is a lot better at scrolling than
>OS/2.
>
>Now, if only I could do the same for OS/2 sessions. My OS/2 windows are now
>10 times slower than my DOS windows at text scrolling (I have timed them).
>
>I find that a little ridiculous to be honest. We have all these fancy
>settings for DOS sessions but are at the total mercy of the OS/Video
>Drivers/Sun Spots when it comes to OS/2 sessions. Is there any way to make
>OS/2 not use software for scrolling and go to the Video Bios. 40 Seconds to
>scroll 128 lines in a window compared to 0.78 seconds full screen (and now
>4 seconds in a DOS window) is totally pathetic.

After I read your post, I was curious to see how fast OS/2 sessions
were compared to DOS sessions, so I ran my own little tests.

I ran a scroll test -- I timed how long it took for the command line
session to print 128 CR-LFs.  I also ran a print test -- how long
it took to print 128 lines of 72 characters (plus the CR-LF to end
each line).

I ran each test for OS/2 and DOS sessions, both FS and Windowed
(maximized).  Actually, there were four types of DOS sessions I used.
Each differed only by different HW_ROM_TO_RAM and VIDEO_ROM_EMULATION
settings.

The video circuitry I have is a Western Digital WD90C31 SVGA.  It has
"Microsoft Windows" (thats what it says in their docs) acceleration
integrated into the mother board, although I ran the tests using the
VGA 640x480x16 driver which I don't think takes advantage of the
acceleration.  Keep in mind that the results of my tests are valid only
for my configuration.  Someone else may get different results.

After I ran the tests I found that although OS/2 sessions are slower
than DOS sessions at scrolling, OS/2 printed as fast as it could scroll.
(i.e. DOS sessions took much longer to print+scroll than to just scroll).
The OS/2 session prints very fast.

For my configuration, setting HW_ROM_TO_RAM to ON for DOS sessions made
them faster (the default is OFF).  Also, clearing VIDEO_ROM_EMULATION to
OFF made DOS Windowed sessions faster, but keeping it set to ON
was made DOS Full Screen sessions faster.

Here are the results of my test:

                       Scroll test   Print test
Session   Sw#1  Sw#2   FS   (Win)    FS   (Win)
=======   ====  ====   ===========   ============
OS/2      n/a   n/a    0.50 (3.35)   0.58 ( 3.88)
DOS       OFF   OFF    1.06 (0.60)   5.72 (10.63)
DOS       OFF   ON     0.90 (6.59)   1.62 (12.22)
DOS       ON    ON     0.78 (6.31)   1.37 (11.50)
DOS       ON    OFF    0.78 (0.35)   1.62 ( 6.53)

[Sw#1 means HW_ROM_TO_RAM, Sw#2 means VIDEO_ROM_EMULATION]

[For each test the first number is the Full Screen result,
 the number in parenthesis is the Windowed result, in seconds]

Also note that sometimes a DOS Windowed is faster than a DOS Full Screen!
And yes, I got an 18.8 (6.59 / 0.35) times faster scrolling just by
changing some settings!

And remember, these results are only from my configuration.  I don't
see how OS/2 can take 40 seconds to scroll 128 lines unless the
video card/circuitry is slow.

>
>-- 
>Tom J Parry.
>Your reality is a figment of my imagination.


-- 
==== Mike Levis   mlevis@ringer.cs.utsa.edu ====
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