akirah

When PSU turn off while computer is on, what happens? any troubles? Or do you have to restart NB?

You'll need to restart computer. The driver will crash and not recover.

Well... depends. I lead the pci-x tape through the ultrabay slot (so I have an empty slot with cable sticking out of it). In general, you can absolutely maintain portability if you don't mind it.

Configuration->Graphics Device->UMA Only

Video Features->Pci Express Graphic->Always Enable PEG: Disabled

I think that's it.

It wasn't SLI, just some BIOS option I didn't switched properly. I tried again and I've managed to disable only internal nvidia keeping intel working.

Interesting results though with 3DMARK Fire Storm

With *only* GTX970 working on external monitor connected to GTX970: Score: 7602 / Graphics Score: 9736 / Physics Score: 6210 / Combined Score: 3295

With iGPU and GTX970, external monitor connected to laptop HDMI: Score: 6633 / Graphics Score: 7321 / Physics Score: 6921 / Combined Score: 3755

With iGPU and GTX970, external monitor connected to GTX970 HDMI: Score: 7781 / Graphics Score: 9542 / Physics Score: 6850 / Combined Score: 3570

Switched to UMA only in BIOS, still can see GT750 in device manager. Disabled 'special features' in video configuration, this completely disabled integrated intel so I can't use Optimus (and monitor works only connected directly to GTX970).

So, how exactly do you disable discrete graphics on this laptop.

I have a pretty much the same configuration with PNY GTX970.