Gigabyte P55A Boards USB3, SATA3 Issues Analysis
 

There are 3 scenarios you could face using that board. One, your graphics card will run at half the PCIe bandwidth (x8) if you use USB3 or SATA3. Two, if your graphics card run at full speed (x16) or if you are on Crossfire/SLI (x8,x8), USB3 and SATA3 will run at half speed. Third, if you are running 3 graphics cards like tri-Crossfire or SLI+PhysX, you can't use x1 slots or the eSATA at all.

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