Dear Intel support team,
I am still looking for an answer.
In the meantime we found some additional information:
"Some motherboards improperly implement centre-spread SSC clocking, which violates the USB 3.0 specification requirements. Centre-spread profiles are centered on the nominal frequency and are modulated above and below by equal amounts, for example +2500/-2500 ppm. Most USB 3.0 devices are not compatible with systems that improperly implement center-spread SSC. When consumers purchase host add-in cards and add them to a system that has a noncompliant system clock, they will be disappointed."
How did you realise the SSC on the DX79SI motherboard?
How can I disable the Spread spectrum Clocking? In case it is not possible, is this function available in an old bios version or with another tool?