Multi GPU graphics card in PCIe x8 slot

[billblog]

I have a gtx 590 and it is currently in a x8 slot not a x16 slot. I know normally the difference between x8 and x16 is minimal, but the difference between x8 and x4 is quite large. Because my card is a dual gpu card does this mean as it is in a x8 it will run as x4 x4, and if so how much of a performance drop can I expect?
Because of my PC layout it is quite hard for me to use the x16 slot.

 

[Tonester0011]

 

[Kaapstad]

It will still run x8

I have a pair of GTX 590s and one of them runs @x8 but it makes hardly any difference.

 

[KillBoY_UK]

My 670's 4gb are in 8x the difference is quite small

 

[billblog]

Thank you, I'll keep it in the x8 then.