cuda motherboard support

hi all,

sorry if this is a stupid question but i just want to check that all makes of motherboards that have pci-e ports support cuda also i have been looking for m/b thats have 3 x16 pci-e ports which i believe that this will be quicker for the 3 gtx275 im planning on buying for gpu processing but all i can see is m/b’s with dual x16 or x16 x8 x8 etc will having card in x8 ports lower the processing speed of the gpu’s

many thanks