mmshah@athena.mit.edu (Milan M Shah) (03/04/91)
I got sick of the silly border (overscan) color feature of the VGA. Its
epsecially annoying because I use a 'dos shell' to execute programs, and this
always screws up the border color for a very disturbing look. So, after a lot
of hacking, I have come up with a small (29 bytes when assembled!!) program
that disables the border color altogether (ie, its always black). Of course,
there's a catch. It works *only* on a Paradise VGA 1024 card based on the
PVGA1B or Western Digital WE90C00 chipset. (from what I know, any card that
is a Paradise / paradise clone made after 1986). Here is the assembly source
for it.
;*****************************************************************************
;
;Author : Milan Shah
;Date : 3/3/91
;Program to disable the border color on Paradise 1024 cards based on the
;Western Digital WD90C00 / Paradise PVGA 1B chipset
;
;*****************************************************************************
_TEXT SEGMENT PUBLIC 'CODE'
ASSUME CS:_TEXT,DS:_TEXT
ASSUME ES:_TEXT,SS:_TEXT
ORG 100H
START: jmp main
;*****************************************************************************
;
; The following code was pieced together with information from 'Advanced
; Programmer's Guide to Super VGAs' by George Sutty and Steve Blair, Brady
; Books, Simon and Schuster.
; Relevant information:
; I/O port 3CEh is the index register and I/O port 3CFh is the data
; Relevant information:
; I/O port 3CEh is the index register and I/O port 3CFh is the data
; register for the Graphics Controller. Index 0Fh of this file is to be set
; to 05h to unlock extended registers. In addition, index 29H of the
; CRT Controller (Index at 3D4h, data at 3D5h) must be set to A5 to
; access indexes 2Ah - 30h of the CRT Controller registers. Index 2Eh of
; the CRT controller registers is Misc. Control 1. Bit 0 of Misc. Control
; 1 disables the border.
;
; To address index i of register file located at I/O port XXXh, first write
; out the index at XXXh, then read or write the data at XXX+1h. Can combine
; the two operations for a write by sending out the word dih to XXXh. Thus
; writing 050Fh at port 3CEh selects index 0Fh and writes 05h into the
; register at that index.
MAIN: mov dx,03CEh ;Extended Register Locking register
mov ax,050Fh ;Index 0Fh, data 05h
out dx,ax ;unlock extended registers
mov dx,03D4h ;Port address of Misc. Control1 Reg.
mov ax,0A529h ;Unlock extended reg index 2A-30h
out dx,ax
mov al,2Eh ;Index 2Eh is Misc. Control Reg 1
out dx,al ;Tell PVGA we want to access it
mov al,2Eh ;Index 2Eh is Misc. Control Reg 1
out dx,al ;Tell PVGA we want to access it
mov dx,03D5h ;Get existing data in Misc Control 1
in al,dx
or al,01h ;Disable the Border bit
out dx,al ;Write Misc. Control 1 data
int 20h ;Done
_TEXT ENDS
END START
I assembled it with Tlink /t. Works like a charm on my machine (clone paradise
1024 card purchased about 2 years ago).
If there's any interest, I can put the .com file somewhere.
Milan
.amead@s.psych.uiuc.edu (alan mead) (03/04/91)
In comp.os.msdos.programmer you write: >... >; The following code was pieced together with information from 'Advanced >; Programmer's Guide to Super VGAs' by George Sutty and Steve Blair, Brady >; Books, Simon and Schuster. Very interesting. I'm looking for good books on VGA graphics and optical disc technology. I'm programming in Turbo Pascal but assembly or C would be OK if they are easy to follow. I am definitely a novice at graphics although I am rather knowledgable about text display and other system features. Have you (or anyone else) any other recommendations? Thanks. -alan mead : amead@s.psych.uiuc.edu
swh@hpcupt1.cup.hp.com (Steve Harrold) (03/05/91)
Re: Removing the VGA border color
Try this 2-line C program:
#include <stdio.h>
main() { puts ("\x1b[50m") ; }
Assembler gurus will want to translate this to a very short equivalent
ASM source code.
This works only if ANSI.SYS or its equivalent is present.
BUT it is screen-hardware independent!!!mmshah@athena.mit.edu (Milan M Shah) (03/06/91)
>Try this 2-line C program: >#include <stdio.h> >main() { puts ("\x1b[50m") ; } Yes, but you misunderstand the intend of my asm program. I am faced with this situation: My normal DOS colors are black letters on white background (ok, you can quit laughing any day now :-) This is done by setting the prompt to an ansi sequence that changes colors, and works quite well. Now, when I execute certain programs for example foxbase, windows etc., all of a sudden my border color gets set to white. Hence the problem is not how to execute a program that turns off the border or sets it to some color, but how to prevent the border color from being changed even if someone tries to set it to a different color. My program will work on a Paradise VGA 1024i, and after you run it once, even if someone tries to set up the border color, the border will not be affected. One might wonder where I ever got software that manipulates the border color. Well, none of the programs I use manipulate the border color, but what happens is that upon entry/exit, DOS sets the border color to whatever was the background color before. If your background is black, there's no problem, but if its not, its quite sinister. Milan .