> -----Original Message-----
> From: Graham North [SMTP:graham.north@LANDINST.COM]
> Sent: Thursday, May 25, 2000 9:39 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [OT]:Video card output in dos?
> 
> Hi all.
> 
> You may remember a post by me asking how many monitors could be powered
> from
> one graphics card.  Well I am still playing with multiple monitors.
> 
> Here is my problem.
> 
> I race model cars and my local club is holding a regional event in a
> couple
> of weeks.  The software used runs in dos (it needs total control of the
> com
> ports).  We would like to have monitors around the track for the refs and
> spectators.
> 
> There is a system we could buy but it would cost over £400.
> 
> My friend suggested the idea of using a TV card with an analogue output
> and
> send the picture via coax to portable TV's set up around the track.
> 
> What I am trying to ask is whether there will be an output from the card
> while the dos software is running?
> 
> Sorry for the long post, hope someone can help me on this.  If you have
> any
> other ideas how I could do this then please let me know.
> 
> Thanks
> 
> Graham North
> 
The answer is a definate maybe.  I have an NVIDIA Riva128 card with TV out,
and also an ATI Expert@Play (Rage Pro chipset I think).  TV out works OK,
under windows, but when the PC is booting and still in text mode, my TV
(addmitedly rather ancient) dosen't seem to be able to handle whatever
refresh rate the card is giving out, I get a flickering, rolling picture
(maybe defaulting to NTSC?).  I've not tried booting striaght into DOS which
I imagaine would give the same results, but I can use a DOS box under
windows.

The composite output is a 50 Ohm source which must be correctly terminated.
You can't just feed it to lots of TV's without serious picture degradation
(and it's bad enough to start with)  You will need some kind of distibution
amp, which should be reasonably simple to make using e.g. high speed op-amps
or a discreet transistor design.

So I guess the answer is that it probably depends if the card you are going
to use has some kind of dos support such as a utility run from
autoexec.bat/config.sys to setup the TV mode properly.

Cheers

Mike