Nvidia NFORCE 780I SLI - Manual (Page 25)

Hardware Installation
NVIDIA Corporation
October 17, 2007 | DU-03597-001_v01 15
Note:
If an ATA-66/100 disk drive and a disk drive using any other IDE transfer
protocol are attached to the same cable, the maximum transfer rate between
the drives may be reduced to that of the slowest drive.