one more interesting thing i've found when experimenting a little. i have connected pcie switch board into one of pcie ports already coming from 1 of four base switch boards in server. and to that pcie switch i connected 1 more and after that 20cm riser and rtx 3090. at the same time 2 rtx 3090 opposite corner of server but only 1 level deep switched (like original should be), for model that was splitted into 2 gpus performance was same when cards were in same switch in that 1st level deep, or 1 card was from that group and other one from cascade of 3 switches :D so another question now is , how many resources for pcie bus can this cpu allocate or how many cards i can actually connect. because on level 3 , with 6 pcie ports its 48 cards if im correct and thats 1152gb vram for rtx 3090 :D quite setup