Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : QWHITE13.ZIP
Filename : DVHERC.TEC

ID:DH Hercules Cards and DESQview
Quarterdeck Technical Note #203 Filename: DVHERC.TEC
by Russell Bell CompuServe:
Last revised: 2/07/92 Category: DV

Subject: Using the DVHERC.COM program to correct problems with running
DESQview on Hercules-compatible monochrome graphics cards.


The purpose of this document is to explain the use of the program DVHERC.COM.
This is a program provided with DESQview that clears up video problems that
some users with Hercules monochrome graphics cards may have.

HOW DO I CURE MY WEIRD HERCULES VIDEO PROBLEMS INSIDE OF DESQVIEW?
If you have a Hercules monochrome graphics card (or compatible) you may
have video problems when you run in DESQview. The user may solve these
problems by loading the program DVHERC.COM before entering DESQview. When the
video problems occur, tap "ctrl-alt-1" (or "ctrl-alt-2", or "ctrl-alt-3", or
"ctrl-alt-4", whichever works) to cure the problem.

WHAT PROBLEMS DOES DVHERC CURE?

DVHERC may address your problem if:

--you are getting the wrong screen, such as when you use the "preview" feature
that many word processors offer, which allows you to view the document as it
will look when printed out;

--you are getting inappropriate blinking or high-intensity attributes;

--the screen comes out blank or garbled.

WHAT PROBLEMS DOES DVHERC NOT CURE?
The DESQview screen blanker fails to blank the top row of dots on
Hercules monitors. DVHERC does not fix this.
RAMFONT (a feature of the Hercules Monographics Plus and Hercules Incolor
video cards) is not supported in DESQview. DVHERC does not help. See the
technote "HRAMFONT.TEC" for some suggestions on what to do.

WHAT IS GOING ON?
Hercules video has a text page and two graphics pages. There is no
completely reliable way to determine which one is current. On real Hercules
cards it is possible to determine which page is current by reading the state
of the light pen port. On a Hercules clone without light pen support DVHERC
is necessary to display graphics without video problems. On Hercules cards
with light pen support the correct page will occasionally not be restored. In
DESQview if a program is using more than one of these pages then the wrong one
may be restored. DESQview may also get the blinking attribute wrong with some
hardware/software.

WHAT DOES DVHERC DO?
DVHERC gives the user the ability to choose which page is used. If
DVHERC is loaded when the user presses "ctrl-alt-1" the text page is
displayed. If the user presses "ctrl-alt-2" the first graphics page is
displayed. If the user presses "ctrl-alt-3" then the second graphics page is
displayed. If the user presses "ctrl-alt-4" then the "blinking enable" bit is
toggled between blinking and high-intensity background.
The "ctrl-alt-4" function, the toggling of the blink enable bit, of
DVHERC works on CGA monitors as well.

EXAMPLES
Say you have used the "preview" function of your word processor. This
causes a graphics page to be used. If you cannot return to the program's text
screen then "ctrl-alt-1" will force the text page to be restored.
If the preview screen comes up blank or garbled then perhaps the wrong
graphics page has been displayed. Pressing "ctrl-alt-2" will display the
first graphics page; pressing "ctrl-alt-3" will display the second graphics
page.
If the blinking attribute is coming up when it should not (or not coming
up when it should) then pressing "ctrl-alt-4" will toggle (switch) how this
attribute bit is set and cure this problem. This feature of DVHERC works with
CGA monitors as well.

NOTE:
All of the actions of DVHERC are completely reversable. Pressing "ctrl-
alt-4" twice returns you to where you were to begin with. Pressing "ctrl-alt-
1" always displays the text page, pressing "ctrl-alt-2" always displays the
first graphics page, pressing "ctrl-alt-3" always displays the second graphics
page. You can look upon ctrl-alt-1,2,3 as a toggle between three different
options; choosing one does not preempt you from using the other.

LIGHT PEN
If your Hercules card has light pen support (and all these cards made by
the Hercules company do) theoretically DESQview will not need DVHERC. It does
not hurt to try DVHERC for graphics problems anyway.

SUMMARY
Most people who are using Hercules have no problems. Those who do should
load DVHERC.COM before entering DESQview and, when their video problems
happen, try "ctrl-alt-1" or "ctrl-alt-2" or "ctrl-alt-3" or "ctrl-alt-4."

************************************************************************
*This technical note may be copied and distributed freely as long as it*
*is distributed in its entirety and it is not distributed for profit. *
* Copyright (C) 1990-2 by Quarterdeck Office Systems *
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