SLI-bridge for video cards: does performance drop significantly without using a piece of hardware?

Question

Iron

Hello.
He helped his brother build a computer based on ASRock P55 Extreme , i3 processor and two Palit GeForce 250 GTS video cards .
The motherboard comes with an SLI-bridge, a piece of hardware for connecting video cards in SLI, in theory. But on the video cards themselves, despite the fact that they are SLI-ready, there were no connectors for it.
After installing the second board, everything started up fine without this bridge (SLI was enabled in the nVidia utility) and the performance of the video subsystem increased noticeably. BUT!
But on the forums and in the old overclockers materials from as far back as 2005, it is stated that the SLI link also works without a bridge, but it starts to lose performance significantly, starting from the 6600GT.
So tell me, please -on modern systems iron SLI-brigde gives performance gain or not? If it does, what kind?
Links to tests with and without hardware (this year) would also help to calm down a lot.
Thank you.

Answer 1

I would recommend you to read:
forums.nvidia.com/index.php?showtopic=117747
At least they seem to write that it is not far behind on the PCIe-2.0 bus (i.e. there is almost no difference).

Answer 2

Just curious - why such a configuration?