Video Card that keeps the DVI/HDMI active?

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I have an ATI Radeon 9250, which has a DVI output.  I have it
hooked to my Sony HDTV while the VGA port is hooked to my PC.
The card is in Clone mode.

The problem is that whenever the TV's video source is switched
away from the DVI input, or the TV is shut off, the DVI output
goes dead and can't be seen again!

ATI says to go into the console app and do a 'detect displays'
every time I switch the TV over to the DVI input.  Is that
ridiculous or what?  I can also bring it back by doing anything
that resets the output, like changing the resolution up and

I just want to be able to have that output active ALWAYS, so
I can switch the TV over to the PC feed whenever I feel like
it (and not have to get out of my La-Z-Boy). I have tried the
ATI feature "Force Display" or something but it had no effect.

Do all makes/models of cards have this limitation?  ATI implied
to me that they all do.

Re: Video Card that keeps the DVI/HDMI active?

"Jorabi" wrote ...
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Is there a better message board somewhere for my question?  No
takers here.

Re: Video Card that keeps the DVI/HDMI active?

On Tue, 07 Feb 2006 15:31:09 GMT, "Jorabi"

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Perhaps if you reworded it for clarity.  We shouldn't have
to think through and figure out what you're talking about
instead of being told clearly.  I'll point out some spots

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Analog output to PC.

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Can you reword that so it expressed exactly what you're

Do you have a mechanical switch?  How is it switched?
Don't answer these questions, reword what you are doing in a
specific scenario that causes the problem.  Don't write
"video source" if you mean you are doing something with your
computer, because it is always the only video source (we
must assume, since you mention no other sources).

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What would you expect to see with the TV turned off?
If you meant that you turn off the TV, then turn the TV back
on and see no video, it would be good to just write that,
not making sweeping generalizations that are too vague.  It
may seem I"m being harsh but remember that you are the only
one sitting in front of this gear and we only have what you
write, not anything else you know, to go on.

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Maybe.  Have you tried setting the DVI device (TV in this
case) as the primary display?

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Have you tried another video card driver?

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What is this "switch the feed" ?  Why are you switching
anything, why can't you just leave it constant and not
"switch", you just turn on the TV or don't?  Or, switch the
TV to the DVI input if the remote allows that?

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What are you switching?  Define specifically what "switch"
means, in actual you-do-what-movement-to-what-thing, even if
that movement is clicking software controls, what is it?

Re: Video Card that keeps the DVI/HDMI active?

OK, let me try my question again.

Are there any video cards out there with a VGA port and a DVI or
HDMI port where the DVI/HDMI port stays active when nothing is
connected to it, or instantly becomes active when a display is
connected to it?  The PC and VGA ports are active and in use
during the time I am asking about.

My Radeon 9250 does not offer this.  It needs to be reset to
get the DVI port to work after connecting a display to it.

Re: Video Card that keeps the DVI/HDMI active?

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The problem is, you will find a lot of video card products are
equipped with the "evil" jack sense functions. The intent is
supposed to be, that by switching off unneeded ports, the
cards are reducing EMI, but I don't know if I buy that or not.
I'm not convinced this function is really necessary.

In any case, you have to consider how jack sense is being done.

On a SVHS/baseband video output, the video card can sense whether
a 75 ohm load is present on the cable.

On a VGA connector, the same 75 ohms sensing can be used on the
R, G, B signals. The same might apply if you had a video card
with component video signals. Any intervening hardware that
screws up the termination of the line, might cause the video
card to conclude that no hardware is present. (A good analog
video switch, leaves unused lines terminated, when you switch
away from an input port. Cheap products leave the line "dangling
in the breeze", and a cheap analog video switch will cause the
video card to disable the output.)

A DVI connector is a good question, as to how detection is done.
A DVI-I connector has both a DVI-D portion and an analog VGA
portion. If a DVI-D device was connected, it would not touch
the VGA pins, so sensing the VGA pins wouldn't work. And sensing
TMDS, and the 100 or so ohm termination at the end of the line,
would not be quite as simple as sensing the 75 ohms of an analog
signal. The sensing function might screw up the signal quality.
That leaves the low speed DDC signals, where the computer can
query the monitor for details about supported resolutions and
the like.

If you use a switching device that interrupts the flow of any
of those DVI-D signals (TMDS data, clocks, DDC serial bus signals),
then I suppose just about any video card is going to have
second thoughts.

In the limited experiments I've done, it seems my VGA connector
is kind of the default, while to get to the baseband TV signal,
I have to fiddle with a control panel. I'm not aware of any
video cards that do the smart thing, and enable ports the
instant that a load appears on the cable. It seems you have
to leave stuff connected, to have a chance to "keep" a
configuration. Which is one of the reasons I wish they would
just shelve this feature.

Good luck,

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