Using VGA to TV converter with Windows 3.1

There are no generic drivers for Windows 3.1 but there are few trics which work at least on some graphics card.

Drivers and WIndows screen

Using VGA to TV converter with Microsoft Windows is harder than with plain DOS. Windows has it's own display card specific drivers which setup the the screen mode and provides the video services to other Windows applications. Making Windows display to work with TV would need the Windows driver to be modified to output the signal suitable for TV. Modifying existing drivers is very hard and getting tools and knowledge to write your own Windows drivers can be even harder.

So usually you can forget getting the normal Windows screen to TV using my circuit unless the driver is configurable enough so you can configure the graphics mode to have TV frequencies and interlacing. Unfortunately Windows 3.1 drivers typically lack this kind of options (if you happen to have those options then it might worth to ry to program 640x480 mode for TV, but you are on your own because those driver configurations are driver specific).

If the driver itself does not support this type of configuration, then you might not have to loose the hope yet. Some (quite many) Windows drivers use BIOS routines to initialize the screen modes, so using driver loaded and activated before running Windows might work if Windows driver uses the resolution supported by the DOS driver (640x480 mode). This method is used in TelevEyes VGA-to-TV Converter drivers which makes possible to use 640x480 standard VGA 16 color mode in TV with Windows 3.0.This type of combination of DOS and Windows driver works sometimes and sometimes it doesn't.

I did some experimenting using VGA to TV DOS driver with Cirrus 542x SVGA card specific drivers and the Windows 3.1 driver with mixed success: the Windows put out 640x480 screen in TV frequencies, but the cursor did not work correctly.

Drivers and DOS sessions

You can use the DOS drivers in Windows full screen DOS sessions to run DOS programs in TV screen. I have used Windows 3.1 for various VGA to TV driver tests, because I can easily switch between TV display DOS session and Windows screen in VGA monitor by just using the normal active window changing key combination ALT-ESC. This is very nice feature in this setup if you can have both TV and VGA monitor connected to VGA card at the same time (you need monitor switch or signal aplifier box for this).

Experiments and results

Windows 3.x in standard VGA mode

TelevEyes VGA-to-TV Converter driver comes with tools to enable Windows 3.0 in standard VGA mode (640x480, 16 colors).

With Windows 3.1 you can set the windoes driver to standard VGA 640X480 with 16 colors. In that mode you can use DOS drivers whic support this graphics mode. Driver called VGASCART have been reported to work with this Windows configuration.

Results with Cirrus 5426 based card and Windows 3.1

Cirrus 542x SVGA card specific drivers support 640x480 mode with 256 colors. I tried this driver with Windows 3.1 equipped with Cirrus drivers. I got the Windows to Tv somehow, but the cursor did not work correctly (because the hardware cursor does not work correctly in interlaced modes) and there were some other minor problems.

MiroCRYSTAL 22SD and Windows 3.11

MiroCRYSTAL 22DS Windows 3.11 drivers have some options user defined timings. There id file timing.ini in driver timign directory. Editing this text file it is possible to change the timings in VGA modes. By adjustung the timings it might ne possible to define a mode which works with my VAG to TV converter circuit. I have not been able to test myself and I have not heard that anyone have made the right TV settings to the setting.ini file.

Tomi Engdahl <[email protected]>