4 monitors

ok, I have 4 monitors, 2 video cards each one on one pci express 16x port
with the same model.

now, my goal is to enable extended desktop, so if I maximize something, it
will be displayed on all 4 screens.

Right now I was just able to enable the maximization to 2 out of 4 screen
using on the nvidia panel span option to use as one video card a total
resolution of 2 displays (2048x768) by each video card. In this case, I can
only maximize any aplication to use up to 2 screens.

The motherboard suppouslly have SLI so acording to the video card
manufacture, I don´t need to put the extra cable between the 2 cards, but Im
not sure if this is the cause of the issue, or if it is the configuration
itself on windows.

Nvidia control panel does not allow me to set the span to all 4 screens.
only up to 2 screens.

teorically I should be able to span or maximize any application to all 4
screens.

Note, I am using same model to all 4 monitors also the same video card.