Not an expert on this but the C: drive should be connected to the first connector numbered on the mobo. Sometimes numbered as zero and sometimes numbered one. Take a close look at your motherboard's details and make sure the SSD is connected to the right connection regardless of the transfer rate. If you have a sata cable rated as 6GB then that would help. Using an ordinary Sata cable reduces it to 3 GB but I think the motherboard should support Sata 3 for the highest tranfer rate and cable to suit.
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