1. you NOT answer for what cards and outputs connected 7 monitors that worked?
they are connected in to the ATI FirePro 2460 and it is trought miniDP to DVI adapter.
2. are you sure that mDP->DVI adapters are ACTIVE????? because with passive adapters you can use only TWO monitors on each videocard!
I am not 100% sure but I have in one card connected three monitors and they are working this mean that they can be active
3. what motherboard you use? what PCI-E configuration?
It is EVGA P67 FTW and I have the VGS in PCI-E 2.0 slots.
4. what PSU you have?
I have 650Watt PSU
5. are you check all 12 monitor work in single mode configuration?
Yes I have all LCDs are working ok in single mode.
this link is not working...
Important: When using mini DisplayPort-to-singlelink DVI adapters, quad output is divided into two pairs (displays 1 and 2, and displays 3 and 4). The displays used in each pair must be identical (with the same manufacturer and model number) and must be identically configured (with the same resolution). The pairs do not have to be identical to each other, however.
according to this and have six different monito models you can use:
4x 24" LCDs Samsung 2443BW on first card (2+2)
3x 27" LCDs iiyama ProLite B2776HDS on second card (2+1)
and 1+1 on third card
max 9 (nine)!
OK NOW I know why I can have problem I didn't know this