yes but i have asus p8z68 vpro and it have 2x pci e (x16 or x8 dual mode) and the black slot is x4 so if i can sli gtx590 in blue and white is it possible
I'm currently using a P8Z68-V PRO with two graphics cards in SLI mode and you can only do SLI using the PCIEX16_1 (blue) and PCIEX_16_2 (white) slots.
The motherboard supports NVIDIA Quad-GPU SLI Technology so of course it will support two GeForce GTX 590's. Just make sure your case is large enough with good air flow and your power supply unit is able to supply sufficient power.
Yes it is possible you can use (blue) and (white) slots for quad sli but there are 3 cpu's for your mobo.
1.core i3 2100
2.core i5 2400,2500,2500k
3.core i7 2600,2600k
which one are you going to use and make sure your psu is enough for 2 gtx 590.