Does Nvidia SLI work correctly on previous generation cards? (The Witcher 3: Wild Hunt)

Spoiler A suspicion has crept in that the SLI configuration on 600/700 series cards has a very low efficiency in The Witcher.
Judging by the posted tests of the cards, the performance of my bundle is no better than one of the same card. Namely, 1080p ~ 15 fps on ultra with gayworks and ~ 45 fps on the lowest possible settings (which is catastrophically low).
The same situation with my friend with a bunch of 760-ok. (he has about 16-18 fps at max)
And how are you?
I do not want to pull the card in order to check ...

My config:
2x GTX660 i53570 4300Mhz 16Gb RAM

Everything is fine, Sli was disabled after updating firewood /facepalm