Using VGA to TV converter with Windows
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 (Matrox Millenium is very good in this). Nowadays many modern drivers have quite sophisticated options for defining used defined monitors. Using this route gives the best result if the setup program can take TV display parameters. Remeber that it is not worth trying more than 640x480 resolution in TV because of resolution limitantions of TV. 480 scanlines fill the entire NTSC picture vertical area, but in PAL picture there is more resolution available (you might try also 800x600 resolution with PAL TV).
If the driver itself does not support this type of configuration, then you might not have to loose the hope yet. Some 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. Usually this type of combination of DOS and Windows driver does not work. I did some experimenting with Cirrus 542x SVGA card specific drivers and the Windows driver with mixed success: the Windows put out 640x480 screen in TV frequencies, but the cursor did not work correctly.
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).
Tomi Engdahl <[email protected]>