Hi,

On Sun, 05 Jun 2016 19:34:15 +0200 lee wrote:
> Hi,
> 
> is there a way to reasonably use two graphics cards with a single
> display?
> 
> SLI won't work because it's retarded in requiring the GPUs to be the
> same, which they aren't --- not to mention that the cards would be too
> far away from each other in the slots for a bridge to fit.
> 
> So what I'm thinking of is like using one card as a default and being
> able to use the other one to play a video in some window on the same
> display, preferably managed by the same fvwm, with the window optionally
> being fullscreen in size.  I'd like to do that because the card I have
> isn't powerful enough to play a video while an open gl application is
> running at the same time.
> 
> I'll probably get a better card once prices come down a bit, but it
> might have the same problem, and why would I want to waste an otherwise
> perfectly good graphics card.

Yes, but it depends on your hardware setup. What's yours and why
you need such unusual thing: connect two video cards to a single
monitor, or do you mean by display X display spawn over multiple
monitors?

In case of laptops such configuration is quite common: they may
have two video cards with single switchable output: intel card is
used for general work to save power and nvidia card is used for
applications, requiring high GPU performance. Switching is done
using sys-power/bbswitch. But looks like this is not your case,
since you are talking about card replacement, since most laptop GPU
cards are not replaceable.

If you want a multihead setup using two cards, this is trivial using
either xinerama or X screens depending on your taste.

As far as I understand your e-mail, you are trying to mux video
outputs of two GPU cards to a single monitor (excuse me if I'm
wrong, but it is hard to understand what your hardware is), this is
also doable if your monitor supports dual input (most modern
monitors do). This way separate X screens may be used to achive
your goal. (Xinerama setup is also possible, but GL acceleration
will be limited to abilities of the weakest card).

But honestly I don't get why you need this: if you have a powerful
GPU and it is not a laptop, where power consumption is critical,
why just don't use that card? Most cards have multiple outputs, so
it is not a problem to setup multihead with a single card either.

Best regards,
Andrew Savchenko