sofakng wrote on 2022-10-19, 00:00:
I’m going to try some of the utilities mentioned but I’m confused how any of the tools can force 15 kHz when it sounds like everybody is saying VGA is always line doubled?
It intercepts the BIOS calls and uses a modified video mode. I´ll post the README from the second utility:
--- The program -----------------
This program allows you to use your TV as a monitor, given that you use the
proper hardware to connect your VGA to the output equipment.
The driver is a TSR (Terminate and Stay Resident) which will try to make
sure your VGA card is, at all times, properly programmed for TV timings, which
are quite different from VGA standards:
- Standard VGA timings are normally 31.469KHz horizontal frequency, and
70.08Hz vertical frequency. Non-interlaced.
- PAL and NTSC are interlaced. PAL (Phase Alternating Line) has a horizontal
frequency of 15.625Khz and 50Hz vertical frequency. NTSC (National
Television Standards Committee) has 15.750Khz and 60Hz respectively.
There will be programs which won't work well, others won't work at all,
because they either use an unsupported video mode, or program the video card
directly, after they've set the mode. Plus, some chipests aren't fully or at
all supported.
Supported resolutions so far: due to the way the program works, resolutions
"per si" are not supported, but rather widths, heights and combinations among
them. This makes the driver more flexible among different SVGA chipsets.
Because of the number of values supported, I won't discriminate them here.
You can find however, a compatibility table on the web site. This table is by
no means complete. More than likely the video cards featured could support
more video modes under VGATV, not to mention other chipsets (albeit with no
interlace support).
Note that since NTSC has less vertical resolution than PAL, modes above 480
lines appear more overscanned than PAL.
--- The requirements ------------
For this to work, you need the following:
a) a IBM PC or compatible computer system (clone for short 😀. And yes,
your 4.77Mhz IBM PC will do. The PCI/AGP card detection uses 32-bit code
which won't run on 286 or less CPUs. Behaviour is undefined if for some
reason VGATV thinks you have a PCI bus on your system;
b) a VGA card. 3D cards only (like the first 3DFx's Voodoos) aren't
supported;
c) some memory to load this driver; if you can run DOS, you can run this.
To save memory, you can try loading it high. Like :
LH VGATV, in AUTOEXEC.BAT
d) an output device like a TV or 15Khz monitor.