Mosaic with sync across multiple Quadro M4000 without additional hardware


we’re currently trying to setup a 3x3 Mosaic with 3 x M4000 cards in one PC.

We don’t have a QuadroSync card installed right now. The Mosaic setup shows missing sync capability for the three cards.
As far as I understand, that’s the expected behavior - and we would need a Quadro Sync card to get sync capability. Right?
Is there any possibility to get the three cards synced without additional sync card?

My colleagues claim they successfully setup such a system before, but they can’t reproduce it anymore - and I can hardly believe that from what I’ve read in the documentation.

We’re running Windows 10 x64 on Dell Precision Workstation with latest drivers from Nvidia.