Ubuntu DVI video port support

[William Chapman]

On 7/25/05, ZIYAD A. M. AL-BATLY <zamb at saudi.net.sa> wrote:
> It worked.  That's Great.
> 
> But I have some notes:  With my current VGA card "MSI GeForce FX 5700
> ViVo 256MB" I can't connect 2 analog monitors at the same time!  One of
> the two must be digital.  And guess what?  DVI has two specifications:
> DVI-D which is digital, and DVI-I which is analog (you can convert this
> one to the normal "VGA-15 pin" through a small kit/dongle that probably
> is shipped with your card/LCD monitor)!  Both specification have the
> same layout/number of pins!  (Most (all?) VGA cards that have DVI port,
> support both types.  However, the other way is not true!  A lot of the
> LCDs found on the market only support the analog interface even though
> they have DVI as their connector (mine is one of those)!)
> 
> Just want to share something that almost drove me crazy not long ago.
> Ziyad.
>
 
Ziyad,

Thanks for sharing!

Of course you are correct about there being two DVI specs, but you
said, "...DVI-I which is analog..."  I think this is incorrect;
actually, the DVI-I interface carries BOTH the digital AND analog
signals.  If you plug the DVI-I cable into a DVI port on an LCD
monitor, it SHOULD BE a "digital deal;" however, because the analog
signals are "in the cable," an adaptor can be used (as you pointed
out) to bring the analog signal out to a standard VGA connector, if
that is the only kind of monitor available.

In this case, the digital signals present in the cable are simply not
used.  Also, I think the number of pins, and the exact pin layout is
different between the two specs.  And there are other subtleties.  In
case you haven't see it, the following link has some pictures and
reasonable clear explanations:

http://www.mycableshop.com/3rd_Level/Video-Flat.htm

HOWEVER, on the other hand, if it is true, as you say, that some LCD
monitors with DVI-I interfaces utilize the ANALOG signals in the DVI-I
cable, and NOT the digital ones, and that this information is somehow
hidden from their customers, then these vendors should marked out and
driven into the sea!!  What is the make and model of your monitor?

Is it possible that your situation could be solved with a different
cable?  (However, most LCD displays come with the "correct" cable for
the monitor.)

Kindly,

Bill Chapman