MS-DOS Drivers

Index

Introduction
Programs
Notes

Introduction

This section shows how to set up the MS-DOS operating system to be displayed in a TV set using the VGA to Scart cable. In some cases this also applies to Windows 3.1, 95 or 98, depending on the video drivers used. The output is PAL or NTSC compatible at 15 kHz.

MS-DOS has no native way to configure the video adapter, so it is necessary to use third party configuration programs. There are many programs for that purpose, in this page I present a list of them with notes from my tests. It is possible that you have to try some of them until you find one that works properly with your adapter.

Standard VGA cards have some features aimed at 15kHz video output, feature that these DOS drivers take advantage of. All video cards are in theory VGA compatible and should work fine but some manufacturers leave out some uncommon VGA features causing compatibility problems.

All these drivers can configure any card to output 15kHz low resolution progressive video (for example text modes or CGA), but to enable interlace (required for high resolution EGA and VGA modes) it is necessary specific support for each card model. If the driver does not support or identify the card it can work without interlace and high resolution modes will look blocky.

Some drivers can work with the standard VGA to Scart cable, however some of them do not set the proper sync polarities and require an additional circuit to correct them. This circuit is known as composite sync adapter and is based on a CMOS 4070 chip to interface horizontal and vertical VGA sync signals to TV composite video input in place of two 1K resistors used in the VGA to Scart cable. The cable required for each program is indicated below.

Programs

Paulo Sérgio Coelho VGA to TV driver - [ Home page ]
This driver is one of the best and offers great compatibility with many video cards. It enables interlace automatically in high resolution modes and works with Windows 3.x, 95 and 98 loading it in the autoexec.bat. It can be set to output PAL and NTSC timings, center the picture and set sync signals polarity (/ISP parameter) for use with standard VGA to Scart cable.

Supported cards: OAK, S3, Cirrus, Trident, Realtek, Intel i81x, UMC, WD, Tseng. Any other card will work without interlace.

Note: Make sure it detects your card type properly, if not force the correct card with a command line switch (see its documentation).

VGA SCART
This driver requires the composite sync adapter circuit, as it does not let you change sync polarity. It allows you to center the picture but you must enable and disable interlace by hand pressing Alt-Left shift-Del. Works with Windows 3.x but interlace must be enabled before execution of Windows. It uses an alternative way to generate interlace that makes it compatible with any card, even though generated interlace is not so good.

Dmitry Skornyakov VGA BIOS Extender
This driver works with the standard VGA to Scart cable since it sets the correct sync polarities, but is compatible only with low resolution modes.

BOFFIN VIP50
This was from a commercial product and requires the composite sync adapter circuit. It does not work with NVidia cards and supports interlace only with Trident, Tseng y OAK. It has to be enabled pressing Alt-V and lets you center the picture, output signal is NTSC.

NTSCVGA: Cirrus driver
Only works with Cirrus Logic cards and requires the composite sync adapter circuit. After each mode switch it is necessary to disable and reenable the driver pressing Control-Shift, works fine with all modes and uses interlace for high resolution modes, but under Windows 3.x the picture gets corrupted easily.

Tomi Engdahl VGA2PAL - [ Home page ]
The PC hangs when run.

Notes

S3 cards only work properly with standard VGA modes. SVGA modes like 640x480 at 256 colours will display only the half left of the picture. This seems an unfixable hardware limitation.

Driver loading can be added into autoexec.bat if a TV is permanently connected to the PC. Most drivers provide some means to enable TV mode automatically.

You can get help for most drivers with command line argument /? or /H.