mzry wrote:That would be slower as the chipset sata controller is connected more directly to the system bus. If you use pci it will not only be limited by the pci bus speed but also by shared resources.
The NB/SB link can push approximately 512MB/s and the PCI bus can push 133MB/s. Max theoretical SATA1 performance is 150MB/s. Most mechanical drives will have a hard time reaching these limits, anyway.
The onboard SATA controller has been known to have compatibility problems, particularly with very modern drives. If you run into such issues, I'd probably look into an IDE-SATA converter rather than a SATA add on card.