I have the new P6N Diamond mainboard from MSI, nVidia nForce 680i SLI chipset.
I have installed 3 cards. If I do independent parallel computations (no communication over CPU) with only two cards (every combination is fine), I get on every card 50 work units per second done which is fine. If I do computations on three cards I get in sum only 105 work units done! the performance of two cards drops down to say 25 and 30 work units. The third card gives full perforamance . This behavior is not static meaning that the perormance drop down is ‘switching’ from card to card. If I kill the third computation on either card, everything is fine again (50+50). Does anybody have this mainboard with three cards ? Does anybody have installed three cards on a board and has experiencded similar things ?
Thank you very much!