Name: 6 Series/C200 Series Chipset Family Desktop SATA Controller (IDE mode, ports 0-3)
DID 1c00 presents ports 0-3 in IDE mode. The controller itself offers 6 SATA ports but the IDE emulation cannot handle them. Hence the split between DID 0x1c00 and 0x1c08.
See the Intel 6 Series Chipset and Intel C200 Series Chipset Specification Update for details